The general public probably just needs basic HTML/CSS/JS support along with gzip, zstd, and common image and video formats. Stuff like beacons, accelerometers, bluetooth, device memory, webusb, battery status, etc. (so basically all of the "platform" part of the "web platform") are either extremely niche or actively harmful.
It really depends on what the big sites they use decide to use. I can see Google using more niche web features just to push people to Chrome.
Do I need accelerometer support to watch a full screen video in landscape on YouTube? That’s probably a big deal for anyone who doesn’t use the app, for example.
Why does this need accelerometer support at all? The OS has that data and can instruct the app to change aspect ratio. Then all the website needs to do is to body.addEventHandler("resize", onresize).