By this standard you should probably not trust any entity at all because all governments are evil and their secret police are after revolutionary troublemakers. I agree that Signal being centralized is a huge problem, but i personally believe the bigger problem is that it requires a unique identifier (the phone number).

We all use centralized services sometimes, for example to sign up on a forum. But when we do so over Tor and with a nickname (pseudonym) that’s a reasonable security practice.