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.
Things matter for their niche. Populations respect Paretian distribution - the worth typically leans on one side -, hence niches matter, hence do their practices.
But why would that interpretation of 'matter' matter?
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.
Edge, a browser that comes bundled with Windows, has 13.55%.