If Firefox dies, it honestly wouldn't be a massive loss for the open web at this point. Webkit and Blink are sufficiently divergent that we would more or less be in the same position we were when Firefox was introduced.
Mozilla's been giving their executives raises while laying off the people who actually make the thing for years now, anyway. It above everything else has sabotaged its ability for long-term survival; no amount of internet rage will change the fact that Mozilla itself does not want Firefox to survive. And its forks would likely survive; Pale Moon has somehow been able to keep at roughly feature parity for ages now despite having forked off a long time ago.
Inspired to research further, I looked and found that Mozilla acquired Pocket in 2017, and it supposedly works on your local-only data for recommendations. Pocket has a subscription plan, and Mozilla as a free software co doesn't have many revenue streams. Them needing to present their product to users doesn't seem that bad viewed in the context of needing a way to support the product. I do think it could be better presented ie explained clearly what pocket is and why they show it to us.