It's not surprising that they're losing in market share. Not sure what they expected when they dumbed down the browser and took away a lot of its capabilities, what made it special, to make it more like Chrome. It's not like people are going to say "I like Chrome, so now that this 'Firefox' browser is similar to it, I'm going to switch." Chrome users are generally speaking more basic users that use it because it's what comes by default on their phones, and because it's everywhere. Whereas Firefox users tend to be more tech-savvy and specifically use(d) it because it suits/suited their specific needs, and therefore would, and did, abandon it when it no longer did so. And then there's the whole ridiculous "accelerated release" where they suddenly started ramping up the version number like crazy, going up a major version about every 6 weeks to keep up with Chrome. I wonder if they're going to just keep going once they hit 100 or if they'll change the scheme somehow to attempt to draw attention away from the ridiculousness of it. They just seem so focused on silly things and doing stuff that drives away users while doing little to attract new ones.
Until recently, I used Waterfox as my main browser, but now I primarily use Vivaldi, though I'm strongly considering switching back to Waterfox, though I'm unsure of the direction of development with that now. It seems there is no good option anymore. Same goes for mobile. Firefox was decent until they completely ruined it several months ago, Vivaldi is far too buggy, Brave isn't much better, and Chrome is, well, Chrome. DDG is decent but isn't really designed for normal use as a daily driver but rather for privacy, which it goes a bit too far on and effectively makes it no good for general use. I've reached the point I just try to use mobile browsers any more than I absolutely have to. I used to enjoy using browsers and surfing the web, but more and more I hate it as they become less functional and more problematic as they try to become overly simplified to appease the masses.