reverted:
--- b/core/core.services.yml
+++ a/core/core.services.yml
@@ -1193,7 +1193,7 @@
       - [setThemeRegistry, ['@theme.registry']]
   theme.initialization:
     class: Drupal\Core\Theme\ThemeInitialization
+    arguments: ['@app.root', '@theme_handler', '@state']
-    arguments: ['@app.root', '@theme_handler', '@state', '%container.modules%']
   theme.registry:
     class: Drupal\Core\Theme\Registry
     arguments: ['@app.root', '@cache.default', '@lock', '@module_handler', '@theme_handler', '@theme.initialization']
diff -u b/core/lib/Drupal/Core/Theme/ThemeInitialization.php b/core/lib/Drupal/Core/Theme/ThemeInitialization.php
--- b/core/lib/Drupal/Core/Theme/ThemeInitialization.php
+++ b/core/lib/Drupal/Core/Theme/ThemeInitialization.php
@@ -54,12 +54,12 @@
    * @param \Drupal\Core\State\StateInterface $state
    *   The state.
    */
-  public function __construct($root, ThemeHandlerInterface $theme_handler, StateInterface $state, $module_list = []) {
+  public function __construct($root, ThemeHandlerInterface $theme_handler, StateInterface $state) {
     $this->root = $root;
     $this->themeHandler = $theme_handler;
     $this->state = $state;
 
-    $this->extensions = $module_list;
+    $this->extensions = \Drupal::service('module_handler')->getModuleList();
     $this->extensions = array_merge($this->extensions,  $this->themeHandler->listInfo());
 
   }