I have found that, as much as Moonchild & Tobin can be difficult, I trust their judgment far more than I do Mozilla's. I want to be in control of my browser, I want to determine what gets downloaded and uploaded from my PC. They tend to be on that side.
Also, my problems with the browser product itself are simple: the UI is awful and cannot be meaningfully fixed, and multi-process programs cause my computer to hang (so I set up a script to auto kill them). Pale Moon respects me as a User, not as an ad profile for Google.
I would never trust the judgement of the most important piece of software on my computer to a small group of tinkerers maintaining a fork of someone else's massively complicated and deeply outdated source code. I don't care who they are—if they don't have a big enough reputation on the line, there's no reason to trust them.
I'm sure your cousin is super trustworthy, but that doesn't mean anyone should put him in charge of the armoured vehicles division of a bank.
Besides, it's a lot easier for a microscopically small and individualistic outfit like Pale Moon to never disappoint you compared to a large, managed entity like Mozilla which has disclosure policies and hundreds of employees each with their own priorities and agenda.
The day I consider my WWW browser the most important software on my PC is the day I go back to dialup. Frankly, I agree with your base theory - that's why the important software on my PC is Windows and MSOffice, rather than *nix and Open or Libre Office. I moved off the OO/LO platform a little after the split, because compatibility was an issue.
But for a limited use program like a browser, yeah, I want the people who won't disappoint me.
Also, my problems with the browser product itself are simple: the UI is awful and cannot be meaningfully fixed, and multi-process programs cause my computer to hang (so I set up a script to auto kill them). Pale Moon respects me as a User, not as an ad profile for Google.