Personally and strictly my own ignorant and informal opinion, Firefox and by extension Mozilla Corp. was doomed the moment it decided to compete with Chrome by being more like Chrome. Firefox built its userbase by being different than the dominant browser, then decided the only way to not die was to be exactly like the dominant browser except with less icky behind-the-scenes privacy behavior. That was a fundamental m…
The challenge with not competing with Chrome is that websites are now mostly developed with Chrome as the dev-tool. Even large companies are just optimizing for that one browser: https://thenextweb.com/dd/2017/11/28/please-build-websites-w... How many users are going to be willing to put up with stuff not working until they switch?
I do use firefox but all the auto-update features are off on desktop. On mobile I am/will be stuck with 68 forever, I suppose as well.