Also FF long time user. Ime FF is pretty much fine nowadays. It used to have problems, but it got a huge leap in performance around 2017 when they improved multithreading support. Since then it is pretty much fine, aside from the occasional awkward unsupporting webpage.

What I do not understand is not why people do not use FF, it is why people use Chrome instead of Chromium, Brave or some other chromium-based browser that is not google or MS. Surely it is not that much more effort to install one of these than chrome.