In "The Mandalorian" series, Ahsoka Tano refuses to train Grogu (commonly referred to as "Baby Yoda") as a Jedi for a couple of reasons:
Emotional Attachment: Ahsoka Tano explains that she senses a strong emotional attachment between Mando and Grogu. Jedi training typically begins at a young age, and the Jedi Order emphasizes emotional detachment to avoid the risk of falling to the dark side of the Force. Ahsoka fears that training Grogu as a Jedi could potentially put him and others in danger if his emotions and attachments aren't properly managed.
Fear of the Dark Side: Ahsoka also mentions that Grogu has already experienced a lot of fear and pain in his past, as revealed in the series. She worries that the strong emotions and potential traumas he carries could make him vulnerable to the dark side of the Force. Ahsoka has seen the destructive power of the dark side firsthand and wants to protect Grogu from that risk.