At first I, like everyone else, downvoted this comment, because "how dare you insult my Servo!", but then immediately took my vote back and then finally was forced to upvote that, because actually I agree. In fact, it's all somehow paradoxically backwards: I liked (I guess I can safely use the past tense now) Mozilla (the company) because of Servo, and Quantum, and Rust, and amazing technical people who made it all happen, not some PR-bullshitters and lawyer-CEO. But I use Firefox (the product), simply because it's only feasible non-Google alternative out there I know, not because it's cooler or even better from the technical perspective. I don't give a fuck what engine they use, Blink and V8 are as fast as it gets. In fact, there was a time before Quantum when Firefox was actually slower than Chromium (and I'm not even sure it's different now, I just don't use it), and I used Firefox anyway. Worse than that, the only place where I actually care about engine performance is mobile, and Chrome just destroys Firefox there. And even then, I opt to use Firefox half of the time (i.e. when I don't need to google smth quickly in the middle of the conversation while moving in the crowd). I guess it's hard to imagine how somebody could use Firefox because of engine at all. It's definitely not the main selling point, by a long shot.

Edit, to summarize: it's not that performance doesn't matter, it's just that currently it's hard enough to compete with Blink & V8. And, of course, Blink becomes better precisely because there is a competition they have to fight. (It will probably become worse when Gecko/Servo/Firefox dies.) But to be that competition without having shitload of money Google has is not fun right now. It's hardly a fight you can win. Easier just to ride on Google's back and to use Blink yourself.