I use Firefox because I'm used to it, I suppose. But I never upgraded beyond ver 90 because they blocked access to FTP sites. Their excuse? Because Chrome did it. They claim to be leaders but they are just followers. If they really wanted to stand out from the crowd they'd support as many protocols as possible, including onion. Instead the tired old excuse is "security".
The other issue is Firefox leaks resources and memory, and has done so for years, and probably will for many more. Just try using Google maps for a while, navigating here and there, changing between normal and satellite views, and eventually it will freeze or get a white screen, or even the dreaded "Gah your tab has crashed".
Still, I don't want to use Chrome and get spied upon and bombarded with ads, and I'm not sure about Edge just yet. I actually trust IE more than those two.