I would say, foremostly, that it’s a dated browser experience. Chrome’s app store is like the Apple app store - it’s the market developers design for first, update first. I would venture to presume that if you are using Firefox you probably aren't using many add-ons/extensions. Because there aren’t that many, and the ones that do exist are rarely (if ever) updated. And if that presumption is true, then you are definitely missing out. Beyond that, what mobile devices do you use? Do you use Firefox on them too? I think Mozilla falls well short of truly great cross-device interoperability, which is a product of a small company working with limited resources - as is their atrocious development cycle. Of course, there’s the bugs and the glitches and the middling speed (which I think is now basically a useless metric in the world of web-browsers, but still very commonly advertised) of a utility that doesn’t altogether do much beyond browse.
I used Firefox years ago, but somehow got hooked on Chrome and now think it’s the uncontested gold-standard. Excepting privacy concerns.
Counterculture tech used to be fun and compelling. Now, more often than not, it's just pretty ****ty. Which saddens me. It's hard to compete with the behemoths.