To me the game is not dark or adult. Their are some society themes, but I don't by default consider them mature. The quality in writing has more to do with maturity than anything.
A kid can bleed and fight in school from bullies and will always find porn around puberty whether you like it or not. Not to mention, at least when I was in school, biology classes start early and are mandatory. Its how things are handled that marks maturity. I think the same concept can be applied to stories. It's not the theme, but how an individual handles the theme.
As for sex, lets not pretend Laezel and especially Minthara are options for normal straight dudes. They are both specific niche fetish's. So let's not go there. Only Shadowheart so far is an option and she is not a swiss army knive of romance. Lol. Not that I'd want her to be.
In highschool I use to tutor at a couple of schools. The elementary schools kids were nastier and more knowledge-able than most adults, but lacked understanding in how to handle most things. Oftentimes I find older people the same way. Only difference is school is now Company or Firm and people are a lot less brave.