Michael Cooney, who never much liked his own voice, distinguished between "singer/performers" and "singer/storytellers" (I don't remember his exact terms), but performers present a song well. They have good training, and can do wonderful things with range and interpretation. Storytellers may not be polished at all, or they may have quite a bit of training and polish, but the difference is that they are singing things that are true for themselves, and are telling stories that matter to them.
I'd say Joan has a wonderful voice -- one I loved particularly when she was young -- and that she is a performer. We can argue about her interpretations and whether we like them or not, and we can enjoy her performances.
Another contemporary lesser known singer (often found in the classical bin) who sings very like Joan is Custer LaRue. If you like Baez, look up LaRue.
If you like story tellers, listen to Michael Cooney, or Rick Lee, Pete Seeger or Anne Lister.
I like both, and for different reasons. For me, listening to a performer is more like listening to classical instrumental music, and listening to a storyteller is more like theater. I confess it, though, my heart is with the storytellers.
Blessings,
Barbara