The whole iMessage/RCS conversation is really only relevant in the US; in other countries basically everyone uses WhatsApp or Kakao or LINE or whatever the local favorite is. In the US, there is no industry-standard RCS. It’s theoretically a carrier-based messaging service but all of the carriers outsourced it to Google so, as an alternative to iMessage, the option is a proprietary extension of RCS running on Google servers, something that is exactly as open as iMessage itself.
If you want a true industry standard way to send messages to people, the iPhone has had that since 2007: email.
I think it’s still very relevant to everyone else. An open standard is better than a closed system like WhatsApp.
One day we’ll wonder why we let so much get tangled up in single companies. You’d think Twitter would wake people up.
RCS the open standard is missing critical features. Google’s implementation fixes that, but is not open. I don’t think we should give a pass to RCS just because it’s open. SMS is a legacy format but it’s unconscionable these days to release a new messaging platform without E2E encryption. That’s a minimum viable product feature, not a maybe nice to have in the future feature.