We didn't use ROCm, the non-ROCm OpenCL path worked fine for us on Polaris and Vega. None of this is a major reason AMD cards are vastly inferior for ML dev and research purposes. At the time they made a decision not to invest heavily in ML framework and workflow support, and so they never had a product really usable for those applications.

I find it annoying they didn't do more but I'm not sure they were wrong. AMD managed to tread water in GPUs, integrate Xilinx, and go from meh to a very strong position on CPUs, and all of that with a relatively small company.