Seriously, YouTube?

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.