Earlier quoted context omitted.
Apparently it's live in the UK and France for Android as of a couple months ago[1], so maybe not entirely dead? 1: https://9to5google.com/2019/07/01/rcs-hands-on-not-quite-ime...
Only one operator in UK (Vodafone) so far. There are about 800+ mobile phone operators around the world and based on reports about 50 or so have signed up. Not a great percentage after 10+ years. And I think the lack of encryption is going to kill adoption in many parts of the world.
Sounds like we might get some movement on this soon, as Google is offering their own servers as a fall-back in the case that the network provider hasn't provided their own.
1: https://www.theverge.com/2019/6/17/18681573/google-rcs-chat-...