Something I've been saying for a long time is that there's a split in open source software, between projects that are true community projects in the spirit of open source (KDE, Deluge) and projects run by an insular organization that happens to release the source code with an open source license because it suits their interests (Android, Windows Calculator).
They both may accept contributions in theory, but in practice the latter projects are exclusively managed by a tiny group of stakeholders in service of their own interests.
Mozilla was increasingly becoming more like the latter type of organization for many years, and is now, I would argue, all the way there. Putting ads in the browser chrome was in some sense the nail in the coffin, because it's not something a community would ever have done to the browser it created and uses.
Personally, the first type of project is what I want to spend my time contributing to.
The unnamed product manager has decided to go ahead anyway
A stark and infuriating contrast from all the democratic-sounding marketing "you can help build the browser of the future/etc." doublespeak that Mozilla loves to evangelise in a lot of places to recruit developers, but then...
https://wiki.mozilla.org/Contribute
"Thanks for your interest in contributing to Mozilla! The Mozilla Project welcomes contributions from everyone who shares our goals"
In other words: "do what we say, or fuck off."