The author seems to conflate "dark" with "adult", so let me take the chance to point out this common mistake. Horror films, Warhammer 40K and 2000 AD comics are all famously dark, but they're for kids or teens. A Midsummer Night's Dream and The Importance of Being Earnest are light but grown-up. It's a weird deformation of the past generation to think that being depressing makes you deep.
Oh, how I agree with your comment!
This is a bizarre trend I've also noticed. Also unfortunately helped with the "adult" monicker for anything showing sex, which is in reality generally more aimed at horny teenagers and so-called "young adults" rather than grownups.