A large part of the problem for Facebook, at least personally, is that its too popular. Initially I only had my college friends on it. With them I had a different dynamic and different kinds of things I'd share. Then the first wave of relatives (cousins, etc) joined. This leads to more content on your feed, but you have to be more careful about what you'd share since its going to reach a different network. Also, its weird if your boss or colleagues want to join your network. Then the oldies joined, parents and grandparents, that means either you set up elaborate rules for who can see what, and remember to set them up every time you update something, or you post bland content that you don't mind anybody seeing. I am not off Facebook, but my engagement has gone down to about a couple of times a week. Their notifications are increasingly meaningless and I am not the only one doing this.
On the other hand, I feel Facebook as a company is doing great. WhatsApp is incredibly popular for exactly the reasons Facebook itself is not, private groups that you can share stuff with as needed. Less chance of people seeing material you did not intend for them.