But you don't need an Apple device to contact iMessage users. Every iMessage ID is a phone number (SMS/RCS) or email.

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?