YouTube itself largely mitigates buffer delays, it uses BBR with TCP and QUIC with UDP, good news for YouTube and its users, but what happens when there's an interaction between bufferbloat-aware flows and other applications? For example, under congestion, my observation is that TCP BBR usually "wins" the game against TCP Cubic/Reno, and is able to utilize a large portion of bandwidth that others couldn't. A 10x increase of throughput is not unseen before, the bandwidth share won't be "fair" until everyone has upgraded. I'm not sure if it's the case for YouTube, but I guess it's a possibility.