Not the OP, but from my perspective, encryption is helpful, but a good portion of security is anonymity, and Signal requires that you use and leak personally identifiable information to even start using it.

It also informs you when people in your contact list are using Signal. It's probably not scanning through all of the phone numbers in Signal's database locally, so it is exfiltrating your contact list as well, exposing your network.

Personally, I'd prefer a model where I am not required to place even that much trust in the messaging provider.