In Romeo and Juliet, both the Nurse and Friar Lawrence are stock characters. Both are Aides and Surrogate Parents who help their respective children. Friar Lawrence is a magical or Supernatural Aide, while the Nurse is a Buffoon, comic relief, a baudy low-comedy stock character who lightens the tragic mood.
Both characters are naive, as naive as the two young lovers. In fact, Friar Lawrence really messes things up for them both, so maybe he's not so good at being a surrogate father (that's why he's a priest). So, I wouldn't necessarily call him knowledgeable. He's rather irresponsible.
The Nurse is not ignorant. I think she's funny and sweet. But, after Romeo kills Tybalt, she betrays Juliet. She says Juliet should marry Paris, even after she's already married to Romeo. What's that all about? In this way, she's not as faithful to her surrogate daughter as Friar Lawrence is to Romeo. At least Friar Lawrence is committed to really messing things up. The Nurse bails on Juliet about half-way through the play.