Facebook makes it easy to curate the appearance of friendship, but meaningful relationships take time and effort in the real world to maintain. People have traded quantity for quality, and the true impetus for this transformation is that social graphs with more nodes are easier for facebook to make money from.

Perhaps hand out an e-mail address and/or something else that does not require people to agree to some corporate ToS/privacy policy where people can reach you to the ones you do care about staying in touch with, preemptively for when they or you stops using Facebook, be it by choice or force.

It is not acceptable that a single or a handful of corps should own the digital social room. If you rely only on them, then it is you who close people out, not the ones who choose to leave or get kicked out.

I get that it's a sad situation but you can not put the blame on the ones who left. Learn from that and you won't have to experience it again.

I guess I am part of your generation as well because I recognize your description.