MMS has terrible limitations, in both file size and media resolution.
RCS has replaced MMS as a protocol back in 2008 and it's only now gaining traction. Many carriers have shut down their RCS infrastructure half a decade ago, though, so they're not exactly jumping on the chance to turn it back on.
Whatsapp felt so responsive back in the day. I'd be pinging my family in real time halfway across the globe on mobile in 2009. For Free. That was a killer app...