RCS has been around for 15 years, but it feels like 15 minutes

Google messages (the only real implementation) still sucks at automatic failover when a data connection is unavailable.

Google Messages RCS is basically flip a coin on delivery if you don't have consistent data for your phone.

Probably because it is worst than any dedicated IM service like whatsapp, telegram, etc

It will randomly fail for a day or two at a time, where all my messages will silently fail to send, without any notification that they failed, and then I check the app hours later and see they need to be resent as SMS.

This isn't really the fault of the protocol itself, but it's infuriating and stops me from recommending it.

Can add too, until it can send in almost any wireless situation like SMS can, it isn't worth bothering with. SMS can send on LTE even when a phone doesn't have a data connection available to the userspace. (Bars but no G icon.) It can send on 2G or above practically instantly. (Although once T-Mobile turns off 2G next year, less of a concern in the US.) SMS is just a raw simple control channel message. RCS is, as others mentioned, just another over-the-top messenger with all the network stack overhead, and a buggy one.

One can fire off an emergency SMS on the side of a mountain with barely usable signal that won't even work for a voice call. RCS would fail in such an environment.

MMS, of course, requires a carrier APN data connection to work, and is a bit slower and more finicky. RCS would definitely be an improvement there.

It has major reliability issues.

Any reliability issues is a major red flag for a protocol that's supposed to supplant SMS, which has no error detection or correction capability, and has a published message failure rate ~12%.

Just visit reddit and look at the kind of issues people have.

Above all else, it's still tied to your cell account. I already have an unreliable messenger tied to a cell account, what value is another one, that after 15 years still has reliability issues, and is dependent on support by a cell carrier (even worse for feature sets)? Being tied to my phone provides zero benefit to me (the opposite actually). So who does it benefit?

No other messaging system is reliant on carrier support/implementation. Why should any messenger be reliant on them, when we have a networking protocol designed to enable apps to be independent of the lower layers?

And before you say using your phone number makes you easy to find, first, other apps use the # as a way to find you, just look at WhatsApp, Telegram, Signal, second, how hard is it really to give someone your contact info? I'm "Bearofatime on lemm.ee". I've given my email and phone number to people verbally a million times, and if it's important, they send a message right then to ensure we're connected.

There are dozens of other messengers out there with zero reliance on carrier support, and work cross platform. They also provide the same features regardless of your carrier.

I was using XMPP on my phone in 2010, messaging people who were on their computers. No dependence on carrier support, no connection to my phone number. When I got to work, I'd login to the same messaging apps on my laptop.

XMPP blows RCS out of the water. So do many other messaging platforms (well, pretty much all of them). So RCS a solution in search of a problem. If it were available to me, why would I use it instead of the other messengers I already use?

As it is I already use multiple messengers, even for work we use 2 or 3, depending on the message.

Mainly that Google essentially owns it now. It's got cool features, but it's reliant on too much bullshit. That's extra true once you factor in that there are services that do the same things, better. Even signal is better, feature wise.

If we're supposed to have some third party company with their nose in our communications, there's better options than Google. It isn't like they've gotten perfect reliability down, they have plenty of lost messages, outages, etc. So, why the fuck bother?