I’ve been using FF for more years than I care to remember, and with the exception of a couple of sites that weren’t really that important, I’ve never had an issue. I certainly never had an issue running uBlock Origin and YouTube.
I flat out refuse to use anything even loosely based on Chromium on principal alone.
Between two evils, Firefox is the comparative good guy. There’s not a chance in hell I’m using anything based on Chromium, I’ve been using FF for close to two decades now and I’ve experienced very few dealbreaker issues.