That's your projection, hence it's your problem.
I've met people who are married when they're 16 or 17. It's a sad, blunt life to live but the country they're in allows such marriage. By 18 they already have their first kid.
Some countries on the other hand have people who marry at the age of 50. If we are in such a country, does that make a person below 50 immature?
Then again that's your projection. The cloud in your mind is the reason why you judge rather than empathize.
We can talk about the harems back in the Mongol Empire. For example, the only nudity scene from the Netflix series Marco Polo that I can find on YT:
https://www.youtube.com/watch?v=v4sqMCpg0f4
This one is much better - the harem scene where they select the girls that can stay in the Great Khan's harem.
https://heroero.com/videos/3559/oliv...o-s01e03-2014/