signal requires a phone number to sign up. a phone number could be used to trace your signal account back to you. so why do people, especially privacy enthusiasts and experts (like edward snowden), still use it and endorse it when it lacks anonymity in that sense? i get that people could use a voip number or something to sign up, but still.
A messenger can at best be pseudonymous, since you want your friends to be able to find you.
And in practice, a mobile messenger that actually works (i.e. makes your phone go “ping” when someone sends you a message, not hours later) will always be traceable to you, as it needs to be able to deliver the message.
Also, regardless whether Signal is perfect or not, it’s the one privacy friendly messenger that people actually use. A messenger where you can reach only your privacy-extremist friends is useless. Signal is already on the extreme end for most people, trying to push anything “more perfect” (but more niche) will just make people use WhatsApp.