It's missing 2 key features that will prevent me from using it and recommending it to everyone I know:
1) No volume control. You could argue this is more a failure of my browser, but it's easier if you just add a volume control. Bonus points if up/down arrows controls work to control it. Really, all the youtube keyboard controls would be helpful here.
2) YouTube sometimes detects my bitrate incorrectly and I need to manually set it to highest. I don't know why this happens, but it does. Let me change that somehow on your site. Even if I have to opt-in to seeing a full youtube player to set it, that's ok.
I would also like a convenient way to get this on my TV. I wonder which android TV devices can install PWAs now.