How so? I use Firefox for all leisure activities, including extensive YouTube usage, and have never noticed any issue. I’m running uBlock Origin and Sponsor Block. I’m logged into a dedicated Google account I made solely for browsing YouTube (so I can keep the viewing history without linking it too obviously to my main Google account).
Page load takes twice as long as Chrome, videos buffer more slowly, and memory usage grows much faster. After a dozen tabs it starts visibly lagging when you press play/pause, the exact same session works flawlessly in Chrome.
It doesn't seem to affect everyone equally. Pretending to be Chrome sometimes helps - not too long ago someone found a piece of code that introduced seconds of busy delay for any non-Chrome user agent.
