CoreML is such a bad lib compared to Pytorch/Jax and even Tensorflow that im not sure why anyone should use it if they can just use other stuff (i would probably prefer pure MPSGraph for training on device at it allows me to control everything in easy and Tensorflow like way)
Highly performant, It runs within docker container. Documentation is highly available.
Challenges: Getting more people to use it and collaborate with it.
SwiftUI has become more trendy, that other frameworks don't get wide relevance.
another library which brings more interesting projects is: CoreML On-Device ML training and inference