“Once lost, users hardly come back until there's a compelling reason, and what would that compelling reason be?” says Bart Willemsen, a VP analyst focusing on privacy at Gartner. Willemsen says he has been a Firefox user since its earliest days. “I think Firefox really has a challenge to find a unique position—not only in marketing statements, but in their absolute product—and go in one direction,” he says.
Firefox did have a unique position: it was the adored child of power-users. Alas, they decided to dilute that position and push for less functionality, more trendy features, more trendy UI and the lowest common denominator.
I, personally, am especially annoyed by how they've gone so hard on this dumbing-down of Firefox for Android, like e.g. you can no longer access about:support anymore for any of the lower-level settings and you're only allowed to install extensions from their miniscule curated list -- no option, whatsoever, for a power-user to ignore such restrictions and accept the responsibility for any resulting issues. That said, the desktop-version of Firefox isn't safe from this dilution and removal of features, either.
It's still the best browser out there, but that position is degrading at a steady pace.