I wouldn’t mind RCS.
I would, however, mind Google’s flavor of it, which is what they’re pushing Apple to adopt.
However, a lot of my problems with SMS magically went away when I switched carriers so a lot of my hate toward SMS may well be misplaced. I still think it’s useful tech, mostly because it doesn’t require a data connection to work like all modern alternatives do.
MMS however needs to die in a fire.