If they won't move off of facebook, I'm not sure there's anything you can do to retain the same level of interaction. Maybe you could allow yourself a reduced level of interaction while still feeling connected. For example, an SMS every couple of days should be plenty enough contact to keep up with any significant events. If you really want to take the reins, you could organise events yourself, ensuring you won't miss them.
It is frequently confused with privacy, however. (https://www.privacyguides.org/en/basics/why-privacy-matters/)
iMessage is the dominant messenger because most people have iPhones combined with the fact that SMS has long been free and unlimited, so people don't see the problem of using it with the occasional Android user.
Really, it's all about the defaults. Even though everyone uses iPhones, they still use the calling feature from their cellular provider, because Apple doesn't push FaceTime as the default calling mechanism.
Signal is gaining popularity because there are people that care about using it over iMessage.
Signal is 100x better than WhatsApp, but it feels so unstable using any centralized messenger that has complete control over the software and the users. No centralized service can truly be relied on, non-profit or for-profit. But clearly that's what has to happen in order for the service to become mainstream, so it's an acceptable compromise for me. It's not like I can't say Signal does great things for privsec and metadata reduction.
Yet I've never felt as though I'm missing out. We communicate via alternative forms (texts, calls, hanging out in person) and I have never felt disconnected.
The whole trope about people being worried about missing out is misplaced - that feeling is exactly what these products are designed to imbue in their users. Ultimately, if you value others, you'll make the effort to connect somehow, and if they value you, they'll return that energy. If that two-way street doesn't exist, if they're not willing to give back a similar effort, then why do we need to know what they're doing or thinking every day?
"I've never had a social media account on any platform and I have plenty of friends and an active social life." Yeah, most people who use social media also have plenty of friends and an active social life.
You seem to not comprehend that there is actual utility to social media for many people, or that most people using social media aren't touch-starved incels or lonely basement dwellers or whatever.
But to answer OP's question since no one else will - maybe try Fediverse alternatives like Mastodon or Friendica.
If you truly feel that judged and offended, and I say this with kindness, perhaps you would do well to ask yourself why.
Hope you have a good day!
Loved your little passive aggressive encouragement to look inward though. So kind.
Or you can do what I did and simply say “fuck it”. Get rid of your account anyway and deal with the consequences. I don’t even have WhatsApp (because, you know, Facebook) but don’t feel like that’s been a detriment to my social life. The people I care about understand and I see most of them on the regular. SMS and phone calls still work. I do know some people who live abroad that fortunately I can communicate via iMessage, but if that weren’t an option then email would have to do. I've been doing this for over a decade and while there was some friction at first, it’s been long since it has been an issue. It probably helps that these days most people understand that avoiding Meta is a good thing.
If you don’t care about people you personally know in your social media, then pick whatever you want depending on features. I recommend Mastodon. It has quirks (what doesn’t) but it’s fine. Chronological (not algorithmic) time-line, open-source, you can even subscribe to people with RSS feeds. If there’s someone you’d like to follow from e.g. Bluesky, there’s often a Mastodon bot for their posts. Or you can subscribe via RSS there as well.
Social is where the accounts are, many of which have a nonhuman substrate with the goal of coercing alignment out of you.