Affected users might have blamed Firefox for the issue. Some may even have switched to a Chromium-based browser, as these worked without any issue.
I've been having issues with YouTube on Firefox for ages, not these issues, different ones. I haven't bothered to test if it's only Firefox that has the problem because I'm not using Firefox for a seamless experience, I'm using because why the fuck would I use anything else on Linux? I won't put google or ms into a Linux environment, even if I don't really care about privacy or whatever, it just feels like mixing oil and water.
Might use another browser like brave or whatever foss solutions are out there, but I'd be surprised if anything like that is better than Firefox.