People often think that Firefox is losing because it doesn't do this one thing they want it to do, and if only Mozilla listened to them they'd see Firefox skyrocketing. Seems like the truth is that Firefox is losing because users don't have a choice.
Both are true. Firefox is losing ground because of multiple reasons It is slower compared to Chromium ones. It is not only slower but more power hungry on mobile phones. Its sandboxing is worse than Chromium. It is less configurable for checkbox-security-applicator Microsoft IT personnel and sysadmins. Mozilla rolls out features, UX changes and removals that constantly annoy its core userbase who can actually install forks of both Firefox and Chromium.
Google has immense power and monopoly over Android phones and the search. Google can also spend practically infinite resources to develop features and force their way into standards. Those features get adopted by developers who are oblivious or ignorant or malicious or simply doing their jobs. Then lack of features reduces Firefox's adoption.
This is nice in theory, but literally never have I heard a friend saying "I tried using Firefox, but it was too slow / too power hungry / had bad sandboxing / wasn't configurable enough". Not once. What I did hear, tens of times, is "I just use X, it came preinstalled with my phone/laptop. Why should I switch?"
I am actually only switching to Chromium based browsers because some corps and most notably some captcha/paywalls don't work as expected. But the. I always think I made the right choice (actually I am rather using Zen because I love their UX on top of FF)
Google has immense power and monopoly over Android phones and the search. Google can also spend practically infinite resources to develop features and force their way into standards. Those features get adopted by developers who are oblivious or ignorant or malicious or simply doing their jobs. Then lack of features reduces Firefox's adoption.