Anecdotally, I'm in my early 20s and none of my friends post to Facebook at all any more -- it is essentially just a messaging app that happens to have your real name in it and a large userbase. I deleted my account and haven't noticed a lick of difference -- in fact, a couple of my friends living far away called me on my phone to ask if I'd deleted my Facebook and tell me that they've deleted theirs as well. Since I did this a couple of months ago I've gotten a lot more texts and calls from acquaintances and friends I used to only interact with in group chats.

So basically if you're feeling trapped by Facebook's social network, remember that it is in fact possible (and often superior) to interact socially outside of Facebook. The tide may be turning.