2.65% global marketshare on statcounter would suggest Firefox doesn't matter.
Its a shame really. But unless something drastic happens, to bring Firefox back into relevancy, I don't see its trend towards obscurity changing.
Edge, a browser that comes bundled with Windows, has 13.55%.
All this says is the majority of people use a mobile phone's default browser.
There is not much real choice when it comes to WWW browsers. For people that refuse Chrome, Safari and Samsung (distrust is sufficient), the 1-digit-percent remainder is the actual solutions space.
So: either things "matter" in practical terms, e.g. choice, which as said can be pretty scarce, so all plausible options are important, or why should the idea of "matter" be important at all.