The “opposite” was just referring to those 2 aspects - Mullvad has stronger anti-fingerprinting which leads to more breakage. Librewolf has that aspect reversed. Of course, both browsers are similar overall. That’s just one detail where they prioritize differently.
Both are good. Librewolf is more like vanilla Firefox, just configured way better by default. Mullvad Browser is like a port of the Tor Browser (also based on Firefox) for the clear web (or for use with Mullvad’s VPN, or whatever). Also configured very well by default. Mullvad Browser has better anti fingerprinting stuff built-in but as a result of its unusual configuration some sites might be broken. Librewolf is kind of the opposite in that regard - sites won’t be broken but you’ll be easier to fingerprint. In any case, they both are at the top of the best Firefox variants I’d say.
The question is wrong: it’s not why do you “still” hate Windows. I did like Windows 7. It was the last Windows I liked. After that, it’s just a downhill enshittification spiral. The only real question is: at which point will it be too oppressive for the common user that even the most common user will try to avoid it entirely. And I fear that there’s still more than enough room for MS to make Windows worse before enough people migrate away from it.