I don't think most people advocating Firefox did it for the extensions. My non-technical family and friends don't care about that.
Firefox used to be just better, obviously better, than what people were using before. Chrome changed that, but still Firefox was the one you could trust not to syphoon your data without your knowledge. It was about having the web not be mediated by a for-profit company that only wants you for your data.
Having competition in the browser-engine space is important, but outside of the HN crowd I don't think most FF advocates did it for that reason. If you didn't suffer IE, it doesn't seem that important.
FF lost because a) it stopped being perceived as better than the competition, b) Chrome took a lot of it's ground through attractive design and marketing, c) Chrome was perceived as better (and I'd argue it was in many respects, at least for a while), and d) Mozilla ended losing a lot of the trust of its previous advocates (with the pocket thing, the Mr Robot marketing stint...).
> Mozilla seems to ultimately draw funding from Google.
I never felt that bad about this point, but may be I was deluding myself. I trusted Mozilla to take Google money without compromising on making FF private and secure.
> t the most interesting challenger browser I'm aware of - Brave, run by ex-Mozilla people - is itself using the Blink engine
Here I agree. There can be lots of innovation in the browser space; may be not the engine, but I'm not sure we totally need it as long as the engine is OSS and there are other companies using it.
Brave does some interesting stuff, but I still would love to see more innovation in how we experience the web. The UX/UI of a browser hasn't changed in a long time.