[grey-area]

This is demonstrably false

And yet you have neglected to demonstrate it. No misanthropy here thanks, you should adjust your assumptions. Perhaps we just disagree on the meaning of the word friend - I'd take it to mean someone who you know outside of FB and via other means of communication, someone who is willing to put in the minimal effort of emailing/texting/calling to contact you individually? Someone who doesn't I would consider an acquaintance at best.

If you make a decision to remain on FB and find it valuable, that's totally fine, but don't try to extend your judgement of its utility and experience of communication to everyone.

[schrodinger]

It's not binary. That someone might still be a good friend, and be willing to communicate by different means for one on one conversations. But it's easy to forget when you're setting up an event and inviting a large group, that one of your friends won't see it and you'll have to contact them individually.