reverted:
--- b/modules/jsonapi_defaults/jsonapi_defaults.services.yml
+++ /dev/null
@@ -1,15 +0,0 @@
-services:
-  jsonapi_defaults.route_subscriber:
-    class: Drupal\jsonapi_defaults\Routing\RouteSubscriber
-    tags:
-      - { name: event_subscriber }
-  jsonapi_defaults.entity_resource:
-    class: \Drupal\jsonapi_defaults\Controller\EntityResource
-    arguments:
-      - '@entity_type.manager'
-      - '@entity_field.manager'
-      - '@jsonapi.link_manager'
-      - '@jsonapi.resource_type.repository'
-      - '@renderer'
-      - '@entity.repository'
-      - '@jsonapi.include_resolver'
diff -u b/modules/jsonapi_defaults/src/JsonapiDefaultsServiceProvider.php b/modules/jsonapi_defaults/src/JsonapiDefaultsServiceProvider.php
--- b/modules/jsonapi_defaults/src/JsonapiDefaultsServiceProvider.php
+++ b/modules/jsonapi_defaults/src/JsonapiDefaultsServiceProvider.php
@@ -19,6 +19,9 @@
     $definition = $container->getDefinition('jsonapi.params.enhancer');
     $definition->setClass('Drupal\jsonapi_defaults\JsonApiDefaultsJsonApiParamEnhancer');
     $definition->addArgument(new Reference('config.manager'));
+
+    $definition = $container->getDefinition('jsonapi.entity_resource');
+    $definition->setClass('Drupal\jsonapi_defaults\Controller\EntityResource');
   }
 
 }
reverted:
--- b/modules/jsonapi_defaults/src/Routing/RouteSubscriber.php
+++ /dev/null
@@ -1,34 +0,0 @@
-<?php
-
-namespace Drupal\jsonapi_defaults\Routing;
-
-use Drupal\Core\Routing\RouteSubscriberBase;
-use Drupal\jsonapi\Routing\Routes;
-use Symfony\Component\Routing\RouteCollection;
-
-/**
- * Listens to the dynamic route events.
- */
-class RouteSubscriber extends RouteSubscriberBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function alterRoutes(RouteCollection $collection) {
-    // Override jsonapi EntityResource controller.
-    foreach ($collection as $key => $item) {
-      if (!$item->getDefault(Routes::JSON_API_ROUTE_FLAG_KEY)) {
-        continue;
-      }
-
-      $controller = (string) $item->getDefault('_controller');
-      if (strpos($controller, 'jsonapi.entity_resource:') !== 0) {
-        continue;
-      }
-
-      $controller = strtr($controller, ['jsonapi.' => 'jsonapi_defaults.']);
-      $item->setDefault('_controller', $controller);
-    }
-  }
-
-}