I switched to Pale Moon after the beta of the most recent legacy add-on switch-off resulted in 8 out of 10 of my extensions being declared "legacy", a few of them refusing to work, and Firefox randomly crashing within a few minutes of opening. I had already reduced my add-ons as I was willing to give the new browser a try, despite repeated protests to the Mozilla. However, the fact so many problems cropped up at once led to it no longer being my main browser. In the past I would have given leeway, but it felt like one change too many despite vocal opposition from users.
That being said, I have no brand loyalty to Pale Moon; the dev seems arrogant and snarky throughout his website, seemingly unable to resist making digs at how his set up and process is superior to Mozilla. It gets tiresome pretty quickly. I have never had a problem with WebExtensions, just their implementation of it, and having more sympathy for devs who have already had to make major rewrites because of Mozilla changes over the last few years. "Proudly" declaring "we will never support WebExtensions" frankly comes across as childish... Meanwhile a whole page is devoted to why having tabs underneath is superior, and why having an add-on bar is superior, before at the very end saying "...But nonetheless you can have it how you want". I prefer tabs on top, I prefer my add-ons to the side of a combined addressbar... Now, by the fact he delivers a product which is now far more relevant to me, I now am happy to use his browser. However, a company with a "head" person with those kinds of attitudes isn't ever going to win my support.
Mozilla, meanwhile, I always have a fondness for. It is fine not to be popular. It just feels the jumble of changes they have made to the browser in the last few years haven't put the user first. When they should.