They just want Castle to be a fun character, I don't see the problem.
I just explained the problem: I think that mystery writers would be more inclined to think critically and see through deception, and thus less inclined to buy into all the supernatural nonsense they keep having Castle believe in, stuff like UFOs and psychics and now ghosts. I think it's a mischaracterization. He already was
a fun character in the first two seasons, but then I gather there was a change in the writing staff in season three and they turned him into this gullible buffoon, which I think is a caricature of how he was originally portrayed. I don't think idiocy is fun, especially in a character who should logically know better.