And you want instead to move the world towards a single, insecure standard, dictated by carriers who have decades long history of (a) supplying data to governments, (b) selling data to random third parties, (c) intercepting messages for their own nefarious purposes e.g. advertising and (d) doing very little to secure and protect their platforms from abuse.
No thanks.
There already is a standard, one which Apple falls-back to when messaging Android: SMS.
The would-be-dystopia you describe well in your second paragraph is not a hypothetical: that is the world as it is today with SMS; Apple could change that by switching to RCS + encryption extension and protect their users' privacy, but they won't because they view it as a competitive wedge (we know this due to the Epic lawsuit, as mentioned in TFA)
Look, I'm not asking for the perfect messaging system here. Because we're never going to get that. I just want something secure and private, and that works by default. Agreed that other client implementors don't have to support E2EE, but Google does, and Apple certainly would, and that covers enough cases right now to make me happy.
I'd grudgingly accept an iMessage app for Android, or (better) iMessage integration with the stock Android app. But I'd much prefer a standard that isn't controlled by a single company's goodwill... goodwill that they have already shown is in short supply.