One of the more limiting things about Signal is you have to give out your mobile number to everyone. Even if it is a burner, I still don't want to advertise to the world that it's mine.
Was happy to read today that Signal is now beta testing a new username feature.
https://community.signalusers.org/t/public-username-testing-staging-environment/56866
Completely private messaging with accounts that have no ties to real-world identities would open the doors to spam and all kinds of abuse.