iMessage is non-interoperable by design. RCS is at least a standard, and better than the existing SMS standard. So it's progress, even if E2EE isn't there yet.
That's a facile argument because nobody uses RCS. RCS failed to gain acceptance, so Google took RCS and built their own app with centralized servers and that's what everybody actually uses on Android. It's basically the same as iMessage, except it requires a phone number.