There are a few reasons:

I haven't compared it in years, but Firefox's bookmark sync is better than Google's, it is a reason why I have stuck with it.

I think Firefox manages hundreds of tabs better than Chrome does as far as memory usage goes. I haven't used Chrome seriously in years, but people continue to complain about how RAM hungry Chrome is so I assume it is still an issue.

But Mozilla has been doing odd things that makes me question them. I would move to some Chromium based browser if ublock origin was... blocked... pun intended... because the web does prefer Chrome over Firefox. If this 3rd party browser is able to integrate some of the functionality of ublock origin that Firefox chose to remove; I would use it over the reasons I listed above in a heartbeat.