Maybe all the features still missing in the Android Firefox played some role ?
Stuff like no print support, no keyboard shortcuts or no tab-bar on tablets ?
Not to mention general extensions support being a shit show as well, with basically just a very small curated list of extensions (mainly add blockers) being supported out of the box.
All of these features were supported by Firefox on Android until ~2 years ago, when they did a rewrite and then ignored requests to bring this functionality back ever since.
A couple links to the Android Firefox open issues:
keyboard shortcuts - https://github.com/mozilla-mobile/fenix/issues/3729
print support - https://github.com/mozilla-mobile/fenix/issues/10217
tab bar in tablet mode - https://github.com/mozilla-mobile/fenix/issues/2344
tablet UX improvements - https://github.com/mozilla-mobile/fenix/issues/4498
[0]: https://github.com/fork-maintainers/iceraven-browser
Oh and it is written in Kotlin. Maybe I should learn it just to try hacking more features in.