Partner Who is “Too Nice”

Hey, guys! So this guy and I have feelings for each other, and he told me he has never been in a relationship before. He said multiple girls have told him he’s “too nice”. I don’t want to ask him to elaborate on it in case it makes him uncomfortable. I’m just wondering if that’s a thing? Like do people actually not like others because they’re too nice? Or is it something deeper, like how niceness can be too much or how some ppl prefer “bad boys”? Idk I’m just really confused, and I’d like to know if this is a red flag before we get into a relationship. Thank you!