Firefox is a great browser and Mozilla is a (generally) great organization. It's my daily driver on all my devices (except my TV ha), it's fast and has great plugins that also work in mobile. Philosophically I'm very much a "root for the underdog" type of person so it makes me happy that way, too. Only very rarely (every few months) am I forced to use Chrome for a site - and in my view, that's a huge ding on the site…
I find this very common with Credit Card and Banking Sites. Very often they either refuse to log me in or log me out sooner than they should on Firefox, or certain pages within the site will just not load. I'm guessing they prioritize security, and only test this stuff in Chrome ;(