I've left mostly because of numbness FB leaves me w/ -- my mind is literally numb from all the hate articles/etc propagated and I see the same crap over and over.
I still have an account, and use messenger w/ wife when she's out and about... but for a social/news 'feed', I've moved over to reddit... the conversations/discussions are a LOT deeper and less assinine (and that's saying something considering some of the culture at reddit can be toxic itself). Plus I can drill down on topics via multi-reddits and such...depending on my mood.
There's also a bit more candor and shock factor on reddit cause of the supposed anonymity people tend to say what they really think even when it's appalling to most other people, so you definitely get a full-spectrum of discussion. It just feels more 'cerebral'.