Revert "Make the New Architecture the default (#43135)"

This reverts commit b9f3186ee6.

packages/react-native/scripts/cocoapods/__tests__/new_architecture-test.rb

@@ -419,10 +419,10 @@ class NewArchitectureTests < Test::Unit::TestCase
         assert_false(is_enabled)
     end
 
-    def test_newArchEnabled_whenRCTNewArchEnabledIsNotSet_returnTrue
+    def test_newArchEnabled_whenRCTNewArchEnabledIsNotSet_returnFalse
         ENV["RCT_NEW_ARCH_ENABLED"] = nil
         is_enabled = NewArchitectureHelper.new_arch_enabled
-        assert_true(is_enabled)
+        assert_false(is_enabled)
     end
 
 

packages/react-native/scripts/cocoapods/new_architecture.rb

@@ -186,6 +186,6 @@ class NewArchitectureHelper
     end
 
     def self.new_arch_enabled
-        return ENV["RCT_NEW_ARCH_ENABLED"] == nil || ENV["RCT_NEW_ARCH_ENABLED"] == "1"
+        return ENV["RCT_NEW_ARCH_ENABLED"] == "1"
     end
 end

packages/react-native/template/android/gradle.properties

@@ -32,7 +32,7 @@ reactNativeArchitectures=armeabi-v7a,arm64-v8a,x86,x86_64
 # your application. You should enable this flag either if you want
 # to write custom TurboModules/Fabric components OR use libraries that
 # are providing them.
-newArchEnabled=true
+newArchEnabled=false
 
 # Use this property to enable or disable the Hermes JS engine.
 # If set to false, you will be using JSC instead.