Firefox worked great for a few months after the big fuss over Quantum coming out and then went right back to just being a browser for enthusiasts and privacy activists. And that's after that whole dumb advertising push they did with billboards reading scary stuff like "Big Browser is watching."
If anything, Firefox is a good example of why it's probably better for aspiring browser competitors to start off by just spinning off from Chromium like Brave did. Not that Brave is perfect either, especially not on desktops, but the saved resources let them focus on finding ways to surpass the competition like improving the mobile ui.
Turning Firefox into a Chrome copycat* with built-in blocklists and Tor Browser Bundle features certainly didn't make it gain more users. Mozilla should've left Brave occupy that space. Brave, Pale Moon and Vivaldi deserve praise.
The thing costing Firefox users is the billion-dollar advertising push and heavy promotion on Google properties. That won’t be changed by trying to satisfy a small number of critics who are not exactly jumping to contribute significant effort to the project, whereas the Mozilla team inevitably has solid answers about maintenance costs bashing their decisions.
If anything, Firefox is a good example of why it's probably better for aspiring browser competitors to start off by just spinning off from Chromium like Brave did. Not that Brave is perfect either, especially not on desktops, but the saved resources let them focus on finding ways to surpass the competition like improving the mobile ui.