From years watching and occasionally contributing a tiny bit to Mozilla, I got that sense.
I understand that creating and maintaining technical documentation takes more resources than most people assume, but there are compromise solutions ...
> it's not like Mozilla itself decided that fmarier's blog was the best place to put this, he just posted it because it's his blog and he's a smart person.
... instead of posting such things to personal blogs, where few people can discover them, how about just posting the exact same things to a central wiki? For the same amount of work by the authors, they would be far more discoverable by people who need the information; the authors would reach a much wider audience. Wiki updates could publish in Planet Mozilla. (I'd make the wiki editable only by Mozilla employees, to reduce the burden on authors who might not want to get into debates with the world over what they post.)
It may not be authoritative documentation, but it would be far better than what's available now and at little additional cost. You can make clear to readers that it's ad hoc documentation (e.g., call it the Beta Wiki, put a notice at the top of each page, etc.), and at the top of each page post the date the page was last revised in a way that nobody will overlook.
Right now you are wasting a lot of great knowledge by hiding it where nobody will discover it; it's like developing great features but hiding them in the interface where nobody will find them.
> Firefox is so friggin' big ...
It is, but to be fair there are many comparable or larger software projects out there where detailed technical documentation is more discoverable. Windows comes to mind.
All easier said than done. Good luck to you guys; you do great work.