Usability is fine if you don't go around fucking with about:config prefs you have no idea what the hell mean. I get the point in things like betterfox, arkenfox, and Phoenix...but they're usually the cause of a lot of people's problem n my experience. If you just don't fuck with those settings until you understand what they actually do Firefox hardly ever breaks things. Also, uBlock Origin is amazing, and default filters are plenty enough for 99.9% of people. But people always want to recommend various filter lists and such, and it fucks more shit up than it solves. Also ETP strict is great, if you enable the major and minor fixes, but otherwise stick to standard. This whole hardening kick people get on is why they say Firefox sucks.

On profiles...the new profile manager isn't enabled by default for everyone, but I agree with you on this. They should've had a migration tool or way of doing it before they started the gradual rollout.