I know that's reductive and perhaps not to the standards of this website, but that's really it for the majority of people who couldn't care less about the diversity of browser engines out there.
I use Firefox for all my ordinary desktop browsing and "it just works" most of the time.
That said I have worked at places that have given up on Firefox compatibility for single page applications. If I've got any choice in the matter I do most of my development in Firefox and let the testers work out problems that turn up in Chrome. However if the app is solidly broken on Firefox I wind up using Chrome like the others.
If a browser fails in some key function even 1% of the time that's enough to drive most users from Firefox to Chrome.
To win back market share Firefox has to be much, much better than Chrome. That's how Firefox won market share from IE in the 2000s and how Chrome won in the 2010s. Firefox feels ever-so-slightly slower to me on loading most web pages and has more failures in loading page elements that I notice than Chrome.
"Just works, most of the time" isn't just works. Just works is perfection or as close to it as software can get.
I know that's reductive and perhaps not to the standards of this website, but that's really it for the majority of people who couldn't care less about the diversity of browser engines out there.