This idea has existed and been implemented for a very long time- Pidgin was the first client I can remember that would try to bridge across various chat networks. You likely are on 14 different chat "networks" already- you might not think of them as chat networks, but as apps with chat functionality.

Just real quick off the top of my head I can name a bunch: FB Instagram Twitter WhatsApp Telegram Signal Gchat/whatever google calls the chat in gmail these days kik sms Irc Discord

This is just a matter of keeping all those separate apps, or consolidating them into one single one. Back in the early 2000s when I did indeed have friends across AIM, Yahoo, MSN, etc... I did use an all in one app to consolidate everything.