in my experience (4 years without "friend"-based social media), becoming disconnected from friends is temporary. during the first year after quitting social media, you will have to work hard to maintain relationships; you will have to instigate social time with your friends through other channels. but after a while, it will start to work in your favor. when those same friends are setting up events on facebook, they'll start to remember that you can only be reached through other channels and they'll start reaching out to you even when they might not have thought to invite you via facebook. and when they want to have a conversation with somebody but don't feel like opening the facebook app, who will they reach out to? you.

my approach was to keep my facebook account, but strip it of everything except my name and a profile picture that says "i don't use fb, please text me". that way, people can still be reminded that i exist and they know i'm always a text message away.