There are people who use Firefox on mobile because it is the only browser to support ad-blocking on mobile , building a unique value proposition and carving a large enough user base for that usecase will allow them to survive.

Yup, but Mozilla apparently does not even care about their Mobile Firefox, they don't advertise that it's one of the only browsers which accepts extensions, and the UI to actually get to add-ons on Mobile is miserable at best. There's so much lack of focus instead of improving what they already have.