In my bubble literally noone uses iMessage. More tech savvy use Signal/GroupMe, less tech savvy use SMS/Email. Family use Signal to chat with me, as I can steer my own family a little.
Also I sometimes open web-interface of Facebook, but any attempts to offer WhatsApp I answer "sorry no Facebook apps on my phone, no Instagram/Messenger either". Never had any issues with that. Although I heard some countries are very dependent on Facebook, so might be hard there.
By the way, I noticed it's not hard to use multiple messengers actually, sometimes it's even faster to find a contact as you always remember what app to look at in recents.
UPDATE: My point is that you can also influence your life and how people communicate with you. Up to a point of course, but it's not like you can do nothing with it.
