I gave up after Ver 28 with constant crashes 2 yrs ago , and went with Maxthon never looked back , as they say if it aint broke leave it alone.
It was 3-4 years back (maybe in the FF 20.xx versions) that I made the switch to Google Chrome. Mozilla was cleanly the #2 browser in the World, then blew it with two buggy releases, to include several sub-versions. Google seized the moment & never looked back, taking many Firefox users for the ride. Most never returned to Firefox, today is a shell of it's former self. Even many of the extension developers conceded after making a public appeal to no avail, there's many that will be dropped sometime around Firefox 55, to possibly include NoScript, one of the best security extensions that any browser offers, as well as their popular download manager in Down Them All.
Firefox was once like the original Opera, with a real community & character, with millions contributing freely to the project, now the browser has fallen due to their own faults, trying to fix things that weren't broken. A couple of days of a bug, I can see & understand, yet 5-6 months is intolerable & idiocy on the part of Mozilla, and that's all it took for Google to step in & takeover their #2 slot.
Like I posted elsewhere, I feel bad for the community who worked tirelessly to build Firefox (many w/out pay), not the corporation. Mozilla did Firefox in, yet it's still open source, anyone can fork the project & take over, only a lot of resources are required to maintain a Web browser. Therefore, while we may see small projects like Pale Moon, don't expect anything huge to become of Firefox's ever shrinking usershare. Stat counters doesn't lie, just like there's proof that fewer 32 bit computers are online, so are less Firefox users. Vivaldi was a surprise project, many took it as default while a Preview, although they had a leg up, were the original Opera developers, so knew the bumps in the road, as well as how to attract a following, have already introduced an email client.
All of this stated also leaves the question of what will happen to an already heavily neglected Thunderbird email client, as well as the SeaMonkey project, an Xfce-like version of Firefox. Thunderbird needs more resources & long overdue. Mozilla seems to be struggling with cash, or that's how it looks to be.