I don't see it as an either-or, but rather a balance to strike. A perfectly private browser with no marketshare doesn't help users. A completely compromised browser with 100% marketshare doesn't help users either.
Mozilla is not happy with us current users though, they would much rather trade us for Edge and Chrome Users..
Mozilla has made it clear it does not value the Users that desire Privacy, Customization, and Power in the hands of the user. Mozilla has Dreams of "beating chrome" a pursuit I have no interest in and place no value in.
The only hope is that one of the forks of earlier versions manages to get enough developers and an institution behind it that they can bring it back to popularity, but before that happens we might be calling the internet "Chromenet" and google won't allow you to visit their sites unless they have been signed with a valid Chrome developer key.
I have used FF since Ver 1.0 for a few reasons the top ones being it is Open Source, it has always been the most privacy and security focused browser, and were strong advocates of Open Standards that where inter-operable on ALL platforms with out vendor lock in
FF is still open source.... the rest that seems to be in flux now.