Is it not really annoying to have four or five different messaging apps to contact different people? How do you keep track of who is on what?
At least with SMS/RCS, I know everybody that I want to contact can receive it.
I can only speak for myself: In my circle, 99% of people are on WhatsApp with a handful on Signal. I have never come across the issue where I didn’t know how to contact someone. There’s badges and notifications, using multiple apps has been a solved problem on smartphones for 10 years.
It would be slightly nicer to have everything in one app, but it’s a non-issue for me at least.
WhatsApp and telegram are currently the best options for most people. I prefer signal but people just won’t use it because they haven’t heard of it