Why down vote an opinion? We are all allowed them.
I’ve used Firefox since before it was Firefox and haven’t witnessed any of the issues you have. As a web developer, I’ve also never had an issue with Firefox requiring special design considerations( looking at you, MS).
I appreciate the fact that Firefox has small share. I have seen what happens when a company and browser become too large and powerful, as Google Chrome has.
Use what works for you.
I remember as a kid, seeing a commercial for a credit card where the clown of the ad tried to use cash, inconveniencing the mob behind him and it really stuck with me how unapologetic credit companies were when training their consumers and debt carriers.