I'm saying that just because mobile device is the majority of devices does not mean that we have to care about them. Rule of the majority is never a good rule.
Depends on who "we" are, from POV of browser vendors and makers of web graphics apps, there's certainly a compromise needed in adding features for niche users that contribute to the combinatorial explosion of tested configurations. Consider that even WebGL 2 currently is struggling to have a viable level of browser support.
WebGL mostly serves people with Intel/mobile GPUs, so will probably WebGPU if it is to survive, even though it aims to do better on the high end GPUs as well.
It would be interesting to see a graphics API designed to cover a range of 100 000x in performance.
Looks like Nvidia TNT had 2 GB/s of memory bandwidth in 1998 and the high end current ones have ~300-600 GB/s. That's just two orders of magnitude difference. Current fast mobile GPUs seem to get 40 GB/s so that plops to about the middle of the historical PC dGPU range, and is just 1 order of magnitude less than dGPUs.