I have been Facebook free for a year (deleted my account) after being inactive for a year prior to that. I've noticed no significant detrimental effects on my social life. I occasionally miss out on inane group chatter and meme sharing on the 'messenger' app, but keep abreast of the more serious discussion during social gatherings with those same friends regardless.
There was a time when my friends were not used to my absence, and forgot to extend me invites to gatherings, though they quickly got better at pinging me a text/calling instead. I much prefer that. I did try to get my small group to switch over to Whatsapp or Signal, but there were a couple of stubborn participants who refuse to leave Facebook and try something new, it never took off, I cope OK without it.
I have noticed much reduced desire interact with my smart phone, part of that resulted from a decision to mute most notifications, I only get text or call alerts. That goes a long way to reduce unwanted or irritating distractions or late night awakenings, technically not FB related, but push notifications are evil
and getting rid of FB was an important step in getting there, as there was no longer a need to be hooked into the news feed.
No more participating in echo chambers or witnessing politically polarising topics and idiotic debates between past acquaintances.
No adverts or temptation to engage hedonistic activity for the sake of it.
No one has access to a trove of data and photos of my misspent youth.
No more third party profiling/harvesting.
No doubt I have now completely lost touch with some distant family and old friends, however those were nothing more than superficial interactions anyway. I don't think that will bother me much on my death bed. Those that still want to make contact can, by other means.
I can no longer follow people or groups that have interesting or meaningful discussions and interactions on the platform.
Lots of photographs are no longer backed up in the cloud (if they did get lost, I wouldn't really miss them anyway).
I recently also deleted my twitter account. Though I didn't use that to interact with friends, I did use it to follow a few interesting people. Instead I'll be doing that only with plain old bookmarks to reduce the effectiveness of cookie tracking/profiling.