Tell me why

I wonder why so many people dislike Albin because he acts like a child? I mean, he's already been through severe trauma from being kidnapped by someone his own family trusted, seeing his loved ones die with his own eyes, brainwashed, and raped. It was also explained by the doctor at the beginning that Albin has some kind of age regression, right? Which makes him act like a child. So why do so many people dislike Albin? But if you don't like Albin and Cinéad's relationship, I understand because I also think it's very strange, because I think they would be more suited to having a siblings like relationship.