I use facebook because everybody else uses facebook. I actually tried to get away from it for years, but I eventually had to, under protest, get back on it because I was too disconnected.
I deleted mine five years ago and I just have a bunch of independent group text threads with family and friends as well as slack/discord. It’s different, and not as conveniently centralized, but it’s certainly not impossible to have a fulfilling social life, go to events, and keep up with people without it. Maybe not so much the third cousin or old family friend. Personally, I don’t feel like I’m missing out on anything positive by not being on it. Meanwhile, I get to avoid being bombarded by ads, opinions I wasn’t interested in, manufactured outrage, and feeling the need to share my every thought with “everyone”.
I've been Facebook (and Instagram)-free for years now, but my personal relationships have suffered for it. Fortunately Facebook is its own worst enemy here, since it keeps making its core products worse and worse for personal relationships. Ads in Messenger, suggested posts, hiding content from friends, dark patterns... it adds up, and over the past couple of years more and more of my friends have abandoned Facebook. Those friendships have largely rekindled. But the heavy users remain jacked in to the News Feed, utterly addicted, to the point where it's difficult to even reach them through another medium.
This is controversial and I always get shot to hell for saying it, but they really aren't worth it. Businesses, friends, even family. If they really require you to use Facebook to talk to them, they don't deserve to be in your life.
After almost a decade off the platform, I still firmly believe that there is no real value there, it's an illusion. It's all held together with FOMO and fear of loss. And you can quite easily lead a fulfilling, happy life without being a part of it.
I do agree with your core point, though: it’s all FOMO, and you can work around everything after you realize that the walled gardens are abusive and not worth your time. I do feel for folks who don’t have good alternatives, though — like families who struggle to find out about school events because they’re only distributed on Facebook. But only by continually insisting that others abstain from walled gardens will we eventually tear the walls down. So it goes; some suffering is inevitable.