iOS does not support RCS so it's dead on arrival.
Back when RCS (under the name of Joyn) was about to be released everybody dreamt of switching to it, thinking that maybe, just maybe, telcos would make RCS free, so you wouldn't have to buy data to chat, like you have to do with whatsapp (back then many people didn't have data). That never happened evidently, and now most people have data because it's gotten much cheaper. So there's no way we will leave whatsapp, and yes RCS is dead.
It'd be cool if we had a standard that everyone could use, like SMS, just that supported larger messages. Oh wait...