Apple doesn't directly compete with CUDA, they just want total control of their platforms. Metal does have great performance and tooling. In practice nobody does HPC on macs so there's no demand for linear algebra or graph libraries, which are a big selling point for Nvidia over AMD.
The fact that Apple is trying to kill OpenGL and OpenCL and block Vulkan definitely sucks though for anyone trying to do indie games, or open source ML/HPC.
Have you looked at OpenGL api's, they are a strange legacy beast. I think Apple does what's best for it's users, even if it has to create a new standard. How about other companies adapting to modern Metal API's instead?
No, you need to use Metal, or Vulkan + Molten VR, both of which suck for compute, but you don't have that much compute available on Apple hardware anyways, so it shouldn't matter that much.
