I'm personally opposed to RCS (it's basically all Google / no real federation, horrifyingly complex because messages can have action buttons and whatnot, and DOES NOT have E2EE despite many implications for years - the newest spec this past year includes it, but nobody does it yet), but SMS and MMS are so incredibly terrible for basically every purpose that I'm entirely fine with attempting to replace it.

But since RCS has become such a mess, and is so anti-competition (you can't make your own app, or servers), I think the answer is now extremely clear: don't use your telecom's messaging system at all, they are all by far the slowest, least reliable, and least private option. App-based messaging is better in almost all practical cases, and I think it's also a healthier future to head towards.