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.
Your green bubble? =P
My social circle is the complete opposite. We're all on iMessage (except for one group of extended family on Messenger), and we like it that way. I was the last holdout for years while I went from Android -> Windows Phone -> Android -> iPhone.
You've listed a whole bunch of alternatives available to you, but for some reason you demand that Apple change its unique offering into just another one of those for you. Why? Is that not a completely enforced monoculture?
Apple has always been off to the side, doing their own thing, and for some reason that fact utterly enrages people. They demand that Apple become just like everyone else. But we already have everyone else! And in every single field Apple is in, there is more of everyone else than there is of Apple.
Have you considered people like Apple products precisely because they're not like everything else? That making Apple indistinguishable from Facebook or Google is no victory, but a significant loss for customer choice?
Thanks to Apple co-opting phone numbers, there's literally no need to ever have iMessage for anyone