I deleted Facebook and Instagram and joined Signal. Not everybody transitioned (instead they wanted me to join WhatsUp lol), but it was a good decision in the long run.
Of course not everybody will transition as well, but let me tell you those who did (in my case) are those who want to be really in contact with you. For the rest I use SMS and E-mail like in the old days haha. You just have to hope that eventually they will join.
It's really hard decision that you have to think about (it took me some time) but I just say "F*** that" and just did it. Until I remove my Fb and Ig they think that I wasn't going to do it but well ^^.