diff --git a/lib/src/generator/templates.runtime_renderers.dart b/lib/src/generator/templates.runtime_renderers.dart
index 2c4095196d..c617f95562 100644
--- a/lib/src/generator/templates.runtime_renderers.dart
+++ b/lib/src/generator/templates.runtime_renderers.dart
@@ -12,7 +12,6 @@ import 'package:dartdoc/src/generator/template_data.dart';
 import 'package:dartdoc/src/model/annotation.dart';
 import 'package:dartdoc/src/model/attribute.dart';
 import 'package:dartdoc/src/model/comment_referable.dart';
-import 'package:dartdoc/src/model/extension_target.dart';
 import 'package:dartdoc/src/model/feature_set.dart';
 import 'package:dartdoc/src/model/language_feature.dart';
 import 'package:dartdoc/src/model/model.dart';
@@ -5089,77 +5088,6 @@ class _Renderer_Extension extends RendererBase<Extension> {
   }
 }
 
-class _Renderer_ExtensionTarget extends RendererBase<ExtensionTarget> {
-  static final Map<Type, Object> _propertyMapCache = {};
-  static Map<String, Property<CT_>> propertyMap<
-          CT_ extends ExtensionTarget>() =>
-      _propertyMapCache.putIfAbsent(
-          CT_,
-          () => {
-                'hasModifiers': Property(
-                  getValue: (CT_ c) => c.hasModifiers,
-                  renderVariable: (CT_ c, Property<CT_> self,
-                          List<String> remainingNames) =>
-                      self.renderSimpleVariable(c, remainingNames, 'bool'),
-                  getBool: (CT_ c) => c.hasModifiers,
-                ),
-                'hasPotentiallyApplicableExtensions': Property(
-                  getValue: (CT_ c) => c.hasPotentiallyApplicableExtensions,
-                  renderVariable: (CT_ c, Property<CT_> self,
-                          List<String> remainingNames) =>
-                      self.renderSimpleVariable(c, remainingNames, 'bool'),
-                  getBool: (CT_ c) => c.hasPotentiallyApplicableExtensions,
-                ),
-                'modelType': Property(
-                  getValue: (CT_ c) => c.modelType,
-                  renderVariable:
-                      (CT_ c, Property<CT_> self, List<String> remainingNames) {
-                    if (remainingNames.isEmpty) {
-                      return self.getValue(c).toString();
-                    }
-                    var name = remainingNames.first;
-                    var nextProperty =
-                        _Renderer_ElementType.propertyMap().getValue(name);
-                    return nextProperty.renderVariable(
-                        self.getValue(c) as ElementType,
-                        nextProperty,
-                        [...remainingNames.skip(1)]);
-                  },
-                  isNullValue: (CT_ c) => false,
-                  renderValue: (CT_ c, RendererBase<CT_> r,
-                      List<MustachioNode> ast, StringSink sink) {
-                    _render_ElementType(c.modelType, ast, r.template, sink,
-                        parent: r);
-                  },
-                ),
-                'potentiallyApplicableExtensionsSorted': Property(
-                  getValue: (CT_ c) => c.potentiallyApplicableExtensionsSorted,
-                  renderVariable: (CT_ c, Property<CT_> self,
-                          List<String> remainingNames) =>
-                      self.renderSimpleVariable(
-                          c, remainingNames, 'List<Extension>'),
-                  renderIterable: (CT_ c, RendererBase<CT_> r,
-                      List<MustachioNode> ast, StringSink sink) {
-                    return c.potentiallyApplicableExtensionsSorted.map((e) =>
-                        _render_Extension(e, ast, r.template, sink, parent: r));
-                  },
-                ),
-              }) as Map<String, Property<CT_>>;
-
-  _Renderer_ExtensionTarget(ExtensionTarget context,
-      RendererBase<Object>? parent, Template template, StringSink sink)
-      : super(context, parent, template, sink);
-
-  @override
-  Property<ExtensionTarget>? getProperty(String key) {
-    if (propertyMap<ExtensionTarget>().containsKey(key)) {
-      return propertyMap<ExtensionTarget>()[key];
-    } else {
-      return null;
-    }
-  }
-}
-
 String renderExtension<T extends Extension>(
     ExtensionTemplateData<T> context, Template template) {
   var buffer = StringBuffer();
@@ -7448,7 +7376,6 @@ class _Renderer_InheritingContainer extends RendererBase<InheritingContainer> {
           CT_,
           () => {
                 ..._Renderer_Container.propertyMap<CT_>(),
-                ..._Renderer_ExtensionTarget.propertyMap<CT_>(),
                 'allFields': Property(
                   getValue: (CT_ c) => c.allFields,
                   renderVariable: (CT_ c, Property<CT_> self,
@@ -7626,6 +7553,13 @@ class _Renderer_InheritingContainer extends RendererBase<InheritingContainer> {
                       self.renderSimpleVariable(c, remainingNames, 'bool'),
                   getBool: (CT_ c) => c.hasModifiers,
                 ),
+                'hasPotentiallyApplicableExtensions': Property(
+                  getValue: (CT_ c) => c.hasPotentiallyApplicableExtensions,
+                  renderVariable: (CT_ c, Property<CT_> self,
+                          List<String> remainingNames) =>
+                      self.renderSimpleVariable(c, remainingNames, 'bool'),
+                  getBool: (CT_ c) => c.hasPotentiallyApplicableExtensions,
+                ),
                 'hasPublicSuperChainReversed': Property(
                   getValue: (CT_ c) => c.hasPublicSuperChainReversed,
                   renderVariable: (CT_ c, Property<CT_> self,
@@ -7779,6 +7713,18 @@ class _Renderer_InheritingContainer extends RendererBase<InheritingContainer> {
                         parent: r);
                   },
                 ),
+                'potentiallyApplicableExtensionsSorted': Property(
+                  getValue: (CT_ c) => c.potentiallyApplicableExtensionsSorted,
+                  renderVariable: (CT_ c, Property<CT_> self,
+                          List<String> remainingNames) =>
+                      self.renderSimpleVariable(
+                          c, remainingNames, 'List<Extension>'),
+                  renderIterable: (CT_ c, RendererBase<CT_> r,
+                      List<MustachioNode> ast, StringSink sink) {
+                    return c.potentiallyApplicableExtensionsSorted.map((e) =>
+                        _render_Extension(e, ast, r.template, sink, parent: r));
+                  },
+                ),
                 'publicInheritedInstanceFields': Property(
                   getValue: (CT_ c) => c.publicInheritedInstanceFields,
                   renderVariable: (CT_ c, Property<CT_> self,
@@ -12632,7 +12578,7 @@ class _Renderer_Package extends RendererBase<Package> {
   }
 }
 
-String renderSearchPage(PackageTemplateData context, Template template) {
+String renderIndex(PackageTemplateData context, Template template) {
   var buffer = StringBuffer();
   _render_PackageTemplateData(context, template.ast, template, buffer);
   return buffer.toString();
@@ -12870,13 +12816,13 @@ class _Renderer_PackageTemplateData extends RendererBase<PackageTemplateData> {
   }
 }
 
-String renderError(PackageTemplateData context, Template template) {
+String renderSearchPage(PackageTemplateData context, Template template) {
   var buffer = StringBuffer();
   _render_PackageTemplateData(context, template.ast, template, buffer);
   return buffer.toString();
 }
 
-String renderIndex(PackageTemplateData context, Template template) {
+String renderError(PackageTemplateData context, Template template) {
   var buffer = StringBuffer();
   _render_PackageTemplateData(context, template.ast, template, buffer);
   return buffer.toString();
diff --git a/lib/src/model/extension.dart b/lib/src/model/extension.dart
index e2f8beea3c..933ec9af97 100644
--- a/lib/src/model/extension.dart
+++ b/lib/src/model/extension.dart
@@ -6,7 +6,6 @@ import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:dartdoc/src/element_type.dart';
 import 'package:dartdoc/src/model/comment_referable.dart';
-import 'package:dartdoc/src/model/extension_target.dart';
 import 'package:dartdoc/src/model/model.dart';
 import 'package:dartdoc/src/type_utils.dart';
 import 'package:meta/meta.dart';
@@ -28,8 +27,8 @@ class Extension extends Container implements EnclosedElement {
       extendedType.instantiatedType is VoidType ||
       extendedType.instantiatedType.isDartCoreObject;
 
-  bool couldApplyTo<T extends ExtensionTarget>(T c) =>
-      _couldApplyTo(c.modelType as DefinedElementType);
+  bool couldApplyTo<T extends InheritingContainer>(T c) =>
+      _couldApplyTo(c.modelType);
 
   /// Whether this extension could apply to [type].
   bool _couldApplyTo(DefinedElementType type) {
@@ -57,7 +56,7 @@ class Extension extends Container implements EnclosedElement {
   Kind get kind => Kind.extension;
 
   @override
-  late List<Method> declaredMethods = element.methods
+  late final List<Method> declaredMethods = element.methods
       .map((e) => modelBuilder.from(e, library) as Method)
       .toList(growable: false);
 
diff --git a/lib/src/model/extension_target.dart b/lib/src/model/extension_target.dart
deleted file mode 100644
index 06b661a952..0000000000
--- a/lib/src/model/extension_target.dart
+++ /dev/null
@@ -1,30 +0,0 @@
-// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import 'package:dartdoc/src/element_type.dart';
-import 'package:dartdoc/src/model/model.dart';
-
-// TODO(jcollins-g): Mix-in ExtensionTarget on Method, ModelFunction, Typedef,
-// and other possible documented symbols that could be extended (#2701).
-mixin ExtensionTarget on ModelElement {
-  bool get hasModifiers;
-
-  bool get hasPotentiallyApplicableExtensions =>
-      potentiallyApplicableExtensionsSorted.isNotEmpty;
-
-  /// The sorted list of potentially applicable extensions, for display in
-  /// templates.
-  ///
-  /// This is defined as those extensions where an instantiation of the type
-  /// defined by [element] can exist where this extension applies, not including
-  /// any extension that applies to every type.
-  late final List<Extension> potentiallyApplicableExtensionsSorted =
-      packageGraph.documentedExtensions
-          .where((e) => !e.alwaysApplies)
-          .where((e) => e.couldApplyTo(this))
-          .toList(growable: false)
-        ..sort(byName);
-
-  ElementType get modelType;
-}
diff --git a/lib/src/model/inheriting_container.dart b/lib/src/model/inheriting_container.dart
index cacdebc8a8..b929164ea7 100644
--- a/lib/src/model/inheriting_container.dart
+++ b/lib/src/model/inheriting_container.dart
@@ -8,7 +8,6 @@ import 'package:collection/collection.dart' show IterableExtension;
 import 'package:dartdoc/src/element_type.dart';
 import 'package:dartdoc/src/model/comment_referable.dart';
 import 'package:dartdoc/src/model/container_modifiers.dart';
-import 'package:dartdoc/src/model/extension_target.dart';
 import 'package:dartdoc/src/model/language_feature.dart';
 import 'package:dartdoc/src/model/model.dart';
 import 'package:dartdoc/src/model_utils.dart' as model_utils;
@@ -74,8 +73,9 @@ mixin Constructable on InheritingContainer {
 /// * **instance**: As with [Container], but also includes inherited children.
 /// * **inherited**: Filtered getters giving only inherited children.
 abstract class InheritingContainer extends Container
-    with ExtensionTarget
     implements EnclosedElement {
+  InheritingContainer(super.library, super.packageGraph);
+
   DefinedElementType? get supertype {
     final elementSupertype = element.supertype;
     return elementSupertype == null ||
@@ -138,7 +138,6 @@ abstract class InheritingContainer extends Container
     ];
   }
 
-  @override
   late final DefinedElementType modelType =
       modelBuilder.typeFrom(element.thisType, library) as DefinedElementType;
 
@@ -258,7 +257,21 @@ abstract class InheritingContainer extends Container
               as Library) as TypeParameter)
       .toList(growable: false);
 
-  InheritingContainer(super.library, super.packageGraph);
+  bool get hasPotentiallyApplicableExtensions =>
+      potentiallyApplicableExtensionsSorted.isNotEmpty;
+
+  /// The sorted list of potentially applicable extensions, for display in
+  /// templates.
+  ///
+  /// This is defined as those extensions where an instantiation of the type
+  /// defined by [element] can exist where this extension applies, not including
+  /// any extension that applies to every type.
+  late final List<Extension> potentiallyApplicableExtensionsSorted =
+      packageGraph.documentedExtensions
+          .where((e) => !e.alwaysApplies)
+          .where((e) => e.couldApplyTo(this))
+          .toList(growable: false)
+        ..sort(byName);
 
   @override
   List<ModelElement> get allModelElements => _allModelElements;
@@ -281,7 +294,6 @@ abstract class InheritingContainer extends Container
 
   String get fullkind => kind.toString();
 
-  @override
   bool get hasModifiers =>
       hasAnnotations ||
       hasPublicSuperChainReversed ||
@@ -544,19 +556,19 @@ mixin TypeImplementing on InheritingContainer {
       // the superchain and publicInterfaces of this interface to pretend
       // as though the hidden class didn't exist and this class was declared
       // directly referencing the canonical classes further up the chain.
-      if (interfaceElement is InheritingContainer) {
-        if (interfaceElement.publicSuperChain.isNotEmpty) {
-          interfaces.add(interfaceElement.publicSuperChain.first);
-        }
-        interfaces.addAll(interfaceElement.publicInterfaces);
-      } else {
+      if (interfaceElement is! InheritingContainer) {
         assert(
-            false,
-            'Can not handle intermediate non-public interfaces created by '
-            'ModelElements that are not classes or mixins: $fullyQualifiedName '
-            'contains an interface $interface, defined by $interfaceElement');
+          false,
+          'Can not handle intermediate non-public interfaces created by '
+          "ModelElements that are not classes or mixins: '$fullyQualifiedName' "
+          "contains an interface '$interface', defined by '$interfaceElement'",
+        );
         continue;
       }
+      if (interfaceElement.publicSuperChain.isNotEmpty) {
+        interfaces.add(interfaceElement.publicSuperChain.first);
+      }
+      interfaces.addAll(interfaceElement.publicInterfaces);
     }
     return interfaces;
   }
@@ -566,12 +578,12 @@ extension on InterfaceElement {
   bool get isDartCoreObject => name == 'Object' && library.name == 'dart.core';
 }
 
-extension DefinedElementTypeIterableExtensions on Iterable<DefinedElementType> {
-  /// Expands the `ModelElement` for each element to its inheritance chain.
+extension DefinedElementTypeIterableExtension on Iterable<DefinedElementType> {
+  /// Expands the [ModelElement] for each element to its inheritance chain.
   Iterable<InheritingContainer> get expandInheritanceChain =>
       expand((e) => (e.modelElement as InheritingContainer).inheritanceChain);
 
-  /// Returns the `ModelElement` for each element.
+  /// Returns the [ModelElement] for each element.
   Iterable<InheritingContainer> get modelElements =>
       map((e) => e.modelElement as InheritingContainer);
 }
diff --git a/test/mustachio/foo.runtime_renderers.dart b/test/mustachio/foo.runtime_renderers.dart
index 55f0822775..6f64562069 100644
--- a/test/mustachio/foo.runtime_renderers.dart
+++ b/test/mustachio/foo.runtime_renderers.dart
@@ -12,7 +12,6 @@ import 'package:dartdoc/src/generator/template_data.dart';
 import 'package:dartdoc/src/model/annotation.dart';
 import 'package:dartdoc/src/model/attribute.dart';
 import 'package:dartdoc/src/model/comment_referable.dart';
-import 'package:dartdoc/src/model/extension_target.dart';
 import 'package:dartdoc/src/model/feature_set.dart';
 import 'package:dartdoc/src/model/language_feature.dart';
 import 'package:dartdoc/src/model/model.dart';
diff --git a/tool/mustachio/codegen_runtime_renderer.dart b/tool/mustachio/codegen_runtime_renderer.dart
index c074a0d163..2c409cca93 100644
--- a/tool/mustachio/codegen_runtime_renderer.dart
+++ b/tool/mustachio/codegen_runtime_renderer.dart
@@ -89,7 +89,6 @@ import 'package:dartdoc/src/generator/template_data.dart';
 import 'package:dartdoc/src/model/annotation.dart';
 import 'package:dartdoc/src/model/attribute.dart';
 import 'package:dartdoc/src/model/comment_referable.dart';
-import 'package:dartdoc/src/model/extension_target.dart';
 import 'package:dartdoc/src/model/feature_set.dart';
 import 'package:dartdoc/src/model/language_feature.dart';
 import 'package:dartdoc/src/model/model.dart';