OpenGL is certainly old and warty but it is nothing like X11.

I think people would be ok with Apple dropping OpenGL if they supported Vulkan, but their motivation and desire to lock people into Apple-only APIs is so obvious and transparent... Why would you support it?

At least Microsoft works with third parties and acknowledges the existence of some standards. Apple are always like "Here is the Apple way. I mean, the way. Because there is only Apple. Apple is the whole world and nothing else exists."