I face lossy connections, and QUIC noticeably improves latency: connections establish in just one or zero round-trips and loss doesn’t cause as much re-transmission. Add forward error correction and QUIC makes lossy connections much less painful. This isn’t just for “adtech websites streaming video”: the biggest beneficiaries are networks like Matrix and XMPP.
There are much bigger things to worry about regarding Google’s control of standards: advertising identifiers, high-entropy client hints, etc. all rolling out before the Privacy Budget is what I’d rather focus on. I think there’s a lot of misplaced negative attention on a transport protocol that gives tangible benefits to people with worse connections.