But... Wire has both! With generics, you introduce complexity into the language that everyone has to understand, but that's obviously not true when it comes to having accounts that aren't tied to phone numbers!
Make a list of privacy-preserving things Signal does: the elaborate privacy scheme for user profiles, the special privacy proxy for GIF sharing, the envelope certificate trick they just introduced, &c.
Then go see what other messengers do to provide the same UX.
Depending on the messenger you pick, you will likely not have to give up your phone number, but you will leave the messenger operator with a log of everyone you've communicated with.
If I remember correctly, as a consequence, they store all of your unencrypted contacts on their server, or at least all of your unencrypted Wire contacts on their server. Unlike Signal, which stores nothing about you other than the date your account was created. That may be the "complexity" you're not understanding, in this case.