Maturity in this case implies being able to contextualise nudity.
Particularly in American culture this always seems to come up. photographs of a naked child in a bathtub being scandalous, a father kissing his son, censoring images of a breastfeeding woman and so on.
In my country mixed saunas and nude beaches are a big thing and I've met a lot of people in particular from the US who always seem to think this is in some way sexually creepy. There's nothing more natural than the naked body and genitalia, we all got some. I don't understand how a culture that isn't in some way repressed has to associate every naked body with 'lust'.
You’d think after the 19th century and colonialism, Europeans would be a little less eager to condemn the rest of the world as ethically behind. Alas...your sentiment is an all too common one.
It's basically protestant modernity or whatever you want to call it that's caused this repression, also a European export so it's not like we're not to blame for a good portion of it. Huge chunks of the colonised world actually had fairly diverse and healthy attitudes towards nudity and sexuality before the era of colonisation. Women with Mustaches and Men without Beards is a great book about sexuality in Iran.
But either way today it does seem to be mostly the US which has the kind of influence that Europe had, and I don't enjoy it because it seems to affect our culture in negative ways.