It's not peer to peer though. It's similar to Lemmy and Mastodon where someone hosts an instance and serves video from that. Except with video it gets very expensive, so I don't think server admins want to see a migration happen.
A peer to peer solution would actually be cheaper for everyone involved.
Seems like infrastructure cost is a central problem of video hosting, so features to distribute that cost load among users would be must-have for any video service not bankrolled by a huge corp.
Yeah, if you had users storing the videos locally and a P2P streaming system you could reduce the cost, but I don't think you can implement something like that through a browser.
Technically it's possible, popcorntime worked (or works, I don't know the current state of it) similarly. It would not work properly on mobile though, p2p is very demanding on poor little device.
Yeah, people would accept running a P2P client on their main computer, but a phone has limited resources where running a P2P server has real costs (in battery, metered bandwidth, etc).
Maybe it could work like podcasts in the olden days where your subscriptions get predownloaded when possible, but it's way too many steps compared to YouTube.