https://user-images.githubusercontent.com/94565446/178122681-73db5439-82a2-45c0-a36f-090b8061389d.mp4

The image above is the cape I wanna use but can't, cause of this issue

OptiFine patched the upstream code, resulting in OptiFine capes always taking precedence over vanilla and CustomSkinLoader capes. We also have no plans to fix this