RCS has been available for over 10 years. Apple is being knocked for their half-assed version of interoperability, where the iPhone implements just enough of the standard to shame non-iPhone users when they communicate with friends and family. If you have any doubt this is intentional, see the emails and public comments from Apple executives.

Interoperating? Is the iMessage spec public? Can I use iMessage on an android phone without hacky workarounds like using a mac computer?

Come to think of it, the same lack of interop openness applies to airdrop, use of the on-phone NFC chipset (for uses other than apple-pay), and a bunch of other such things.