You're going to hang the state of networked browser gaming on this random person's netcode implementation? Go to r/GameDev and you can find some redditor Unity projects built on UDP that are even worse, but you aren't going to say "wow, UDP sux".

Check out something like https://krunker.io/ which gives me a surprisingly good FPS experience despite my distance from the server.

Browser gaming does take some thought though, to be sure. UDP via WebRTC is relatively new and isn't trivial. And I know some games get around TCP head of queue blocking by opening up 2+ WebSockets.