The primary advantage of QUIC for things like congestion control is that companies like Google are free to innovate both sides of the protocol stack (server in prod, client in chrome) simultaneously. I believe that QUIC uses BBR for congestion control, and the major advantage that QUIC has is being able to get a bit more useful info from the client with respect to packet loss.

This could be achieved by encapsulating TCP in UDP and running a custom TCP stack in userspace on the client. That would allow protocol innovation without throwing away 3 decades of optimizations in TCP that make it 4x as efficient on the server side.