(Not to object the degoogeling, but:) To create a Signal account, you have to validate a phone number. So Signal is currently largly about privacy, not anonymity.
FWIW I wouldn't know why to message someone if I didn't know who they were. The same goes for them not knowing who I am. What would we even talk about?
The service operated by the incorporated 501c3 has full visibility into who else a user messages and when. This is not good for privacy.
What the non-low-value users are generally looking for is the option to not opt-in to discard anonymity with any potentially involved third parties such as server operators and network operators, and left at the discretion of the users solely.
Other systems have already solved this. One user can be not anonymous while another can choose to not opt-in to not be anonymous.
The users still know who the user on the other side is.