Signal is not privacy respecting at all when it still requires a phone number for signups and there are no third party servers.
Their app also links with google play services on android (there is a degoogled release called Molly that I use instead of the main app).
The main benefit of signal is just having access to a un-facebooked WhatsApp that is easy enough to get other people on. I use signal for this reason.
People should check out GNU Jami as a p2p messaging application that requires no signup at all. Or just check out XMPP which requires no phone number or additional credentials besides a username and password.