Earlier quoted context omitted.
I can. I'd still rather use Firefox than Chrome or Edge when it comes to privacy. "Firefox is dead ... Time to bury the putrid, rotting corpse" is ridiculously dramatic.
Mozilla as an org is a husk of it's former self. They're constantly playing catch up with Firefox, almost abandonwared thunderbird, and have little actual usable innovation. What part of Firefox is "open source" when you can't integrate in your own projects? What's the point when the tech is non portable? Chromium is the clear OS winner, so open and modular you can just make your own browsers.
AFAIK, all of it; there are even full independent forks running around. Just because you can't bend the code to your particular use doesn't make it not FOSS.