e.g. i would have never paid for the A/R stuff they distracted their Servo engineers with (plus the Magic Leap entanglement). i would have also withheld funding for the non-removable Pocket integration fiasco. and the jack-in-the-box Mr. Robot promotion - once my tools start to become Mozilla's agents rather then user's agents, they cease to be my tools.
i should add that people who choose to use firefox rather than the default are those who are most likely to pay. not listening to them is absolute nonsense.
1. Mozilla's revenue from the Google search deal depends on users searching for things using Firefox. More searches through the Firefox search bar, more revenue for MoCo.
2. Marketshare == developer mindshare. Declining marketshare has created a positive feedback loop where devs (or their managers) become less concerned about supporting Firefox. This induces more web compat issues, which causes more people to switch away, cycle repeats.
Firefox used to have two major advantages, at least for me as a user rather than a developer: customisability and the respect for privacy. The former went under a bus with Quantum and has never recovered. The latter is still there, but the single biggest hole in it is the use of Google for search, so that's probably the first thing that many privacy-sensitive users are going to change.
I do still use Firefox as my primary browser, despite having reconsidered several times in recent years. However, as a dev I have all the others readily to hand, and I do find myself forced to use others because pages simply don't work in Firefox with noticeable frequency now. From the opposite angle, I also can't remember the last time a client specified Firefox compatibility for a new project. It's usually Chrome, iOS Safari if mobile is relevant, and maybe Edge in corporate settings now.
Unfortunately the vicious cycle of market share and compatibility has been established, and while I think we'll all end up worse off for it, I'm not sure there's much anyone can do about it at this point, at least not as long as most of the actual functionality in Firefox is (unsurprisingly) so similar to other browsers.
I don't think Mozilla/Firefox is failing because no one will pay for it, but, because it won't take money for Firefox directly.