But fundamentally, Firefox decisions are made by Mozilla employees, to further the goals of the Mozilla company (which makes money from those decisions - sure, to be hopefully reinvested). Firefox isn't like those other large open source projects where the codebase and thus decisions are owned by many independent (and mostly commercial) entities. Outside contributors have very little say in the product, so I wouldn't say its any better for people to contribute to Firefox vs e.g. Chrome. I.e. Mozilla wants their code - but in the many cases that have become publicised it doesn't seem like Mozilla wants their opinions.
(This is probably just the reality of end-user facing software projects with major UX components. But it's still sad to see contributors being invited in when they'll be ignored in the decision-making.)
// Edit: and it looks like fabrice_d made pretty much the same point while I was writing my comment : )