Yes, of course, a PWA or web-based solution, ala Google's Stadia, has mainly two -solvable- challenges: controller support, which is done at the OS level in iOS and Macs, but, I dont know ATM if a PWA would have access to the inputs, and second, make use of the correct codec (h265, vp8, etc.) to target the video hardware decoding for minimum latency and best performance. As I said, IMHO these two challenges can be overcomed. Maybe someone with more experience on developing PWA's can step in to give feedback on this.
Just to add a bit of context, my understanding on why Google Stadia launched requiring its own gamepad has to do with it connecting directly to Google's cloud, thus avoiding the issue of receiving the input from the browser's host OS. In that scenario (you connect a special controller directly to the service, the video displays the input) you could run the service on anything with a compatible web browser, compatible meaning supporting hardware acceleration of your chosen codec.