I think the thing Nostr does is make the social graph an accessible, inherent part of the protocol itself.  It used to be the social graph was accessible only through propriety APIs, but since Nostr is an open protocol, that social graph is now available to any application using the protocol.

Of course, that is the exact reason why one would want privacy, but fortunately there are a number of possible ways of preserving privacy, not least of which is anonymity.