It's a good browser! I've used it since the days of mozilla. It's only gotten better. Honestly I really prefer it to chrome. FF mobile is best in class as a mobile browser for the sole reason that it allows extensions like ublock. FF developer edition is, imho better than chrome.
I tried chrome on linux some years back, and experienced an issue where the browser would crash the os on the extensions search page. Years went by without this being fixed. Firefox would never do that.
I use Firefox because it's the better browser in my experience. For me the killer feature is the container thing. I'm not even sure how it's called. So I have different containers with persistent sessions for different purposes. Work/personal/consulting. Makes things much easier when you don't need to juggle gmail/slack/microsoft logins all the time.
I've integrated that into my personal workflows so tightly that I'd be very unhappy if I had to use a browser without that capability.
Last I checked Chrome(ium) doesn't have it. What about Oper... I mean Vivaldi?