> the status quo (SMS/MMS)

There are countries that aren't the US. I honestly don't remember when was the last time I've actually sent an SMS. 99% of SMS messages I receive are notifications and 2fa codes. If anything, "status quo" over here is Telegram and VKontakte.

Besides, the issue with SMS/MMS is that it's a closed system tightly controlled by carriers. The internet is an open system.

In the EU (at least in Romania), MMS is not a thing, and even SMS is not the status quo. Everyone talks using WhatsApp mostly.

SMS stopped to be status quo here (central Europe) because it still costs money to send each single text. It made sense when no other mobile communication option was available (early 2000s) but not anymore. WhatsApp or any other messaging platform is strictly better as long as your phone is connected to the internet.

> So keep the status quo (SMS/MMS) and build more features on top of that ?

what you are describing can be called "iMessage" :)

Those are not extensible enough as they are bound to the transport layer.