This is the first time where I got a visceral feeling that maybe this isn't the browser I knew and loved anymore. It's not like I'm uninstalling and switching to something else, but I do feel bummed out.
https://news.ycombinator.com/item?id=15941302
https://news.ycombinator.com/item?id=15940144
I feel similarly to you...long-time user, bummed out by stuff like this. Sometimes it feels like Firefox would be a lot better off without Mozilla occasionally making deals like this.
There's such a marginal difference between the quality of the two browsers, and Chrome is held back in what it can be by the necessity of furthering Google's commercial interests. The only limit Firefox has had is that they can't abuse the trust of their users. Firefox had to voluntarily (and often aggressively) inflict a huge amount of reputational and functional damage on itself to reduce its market share to the place that it has.
edit: it's important to say that they didn't really backslide technically; it's user-hostile (management) decisions that have hurt the browser, not anything to do with the skill of Firefox developers.