I know they’ve been getting more controlling over time, but blocking an entire browser, really? I’ve been watching YouTube over Firefox for 5+ years now just fine, and now they shut me out arbitrarily? Nah, fuck that.
Edit: It’s something wrong with the new LibreWolf update and my profile. Causes issues in both normal and private browsing, but not a different profile and is solved by switching user agent.
Comically, the error message is a lie. Why lie? … Nobody asked for optimization, right? If it were actually about optimization, the site would work slowly. But they are afraid to admit that they refuse to follow the specifications. Meh.