Hans’s eagerness to visit Naphta despite the fact that Naphta is unpleasant and even seems rather suspect (or “dubious,” as Joachim puts it) shows how naïve and undiscerning he his. He’s unable to differentiate good and helpful knowledge from “dubious” and harmful knowledge and takes everything he learns, whether from Settembrini or Krokowski or Clavdia Chauchat, at face value. When Joachim criticizes Hans for “learning” instead of focusing on getting better, he suggests that Hans’s intellectual curiosity is self-destructive. Implicitly, he's suggesting that Hans’s intellectual pursuits—which remain unorganized, unformed, and abstract—do nothing to improve Hans’s quality of life. Instead, they distract him from what ought to matter: the practical pursuits of getting better and returning to the life and responsibilities he left behind when he came to the Berghof.