I’ve been using using firefox and more recently fennec and mull on android for years now and I’ve never had a problem with it. Why do you think it sucks? Just the fact that you can install extensions on firefox (or fennec or mull) makes it by far the best browser in my opinion. I do agree that firefox by default has some privacy issues but there’s no way it’s worse than chrome which almost everyone uses, and as you said you can just use a fork like mull for best privacy.