I was not familiar with RCS yet but according to Wikipedia, Apple will begin to support RCS in 2024.
On the other hand, this doesn’t exactly inspire confidence that it is going to be a polished experience: „Not all RCS functions defined in the standard are offered by every network and every client; only the services that are available to two communication partners are also offered in the client.“ (translated from the German Wikipedia article).
I’ve had iPhones for ten years and never once cared about RCS. Never even heard of it until recently, and I don’t think anyone I know has ever heard of it. It’s very very niche to care at all about it.
While "RCS" is an obscure standard nobody cares about, "being able to send reactions, high-res photos, videos, and voice memos in text messages" is a pretty universal concern. iPhone support for RCS would let iPhone users have those features in conversations with the green-messages.
I never once wished I was able to do that, the only application for that would be to communicate with android users that for some reason refuse to use whatsapp, fb messages, telegram or any of the numerous cross platform that do that. Why would anyone want to do this specifically using the sms protocol?
The point is that I don’t care about doing these things specifically over SMS. I send photos, voice memos etc over apps like whatsapp. It wouldn’t improve my life one iota to be able to do that with some legacy protocol.
What people care about is doing these things over something that is universal enough. In some places WhatsApp is so pervasive that it's that; in others, a mandated standard like SMS or RCS is the best you can hope for.
On the other hand, this doesn’t exactly inspire confidence that it is going to be a polished experience: „Not all RCS functions defined in the standard are offered by every network and every client; only the services that are available to two communication partners are also offered in the client.“ (translated from the German Wikipedia article).