OP you keep saying derivative, like it's a bad thing. Have you read them, or just watched the film?
No one said only keep your teens reading the crappy teenage stuff churned out - I remember Sweet Valley High and the Point Horrors churned out when I was 11-15. They were dreadful, repetitive crap. In fact, SVH seemed to outright promote sexual violence and an obsession with being a perfect size 8!
I also read Tolkien, Stephen King, Atwood, and many, many other so-called adult books aged 11/12. I was obsessed with Simone de Beuvoir, and read Colette, Rilke, Greene, Cocteau at 13 - so? I read a lot, avidly. That doesn't mean I didn't also enjoy less "literary" writers, less "adult" fiction too. There was a young horror writer I loved called Christopher Pike, who was like a Stephen King marketed for teenagers. Some of his books touched me in a way I still think about sometimes.
I hope my future children read like I did, I learnt and felt so much. But there are many writers out there putting out "derivative" stuff and it's still valid, still good within it's own right. I didn't particularly get much out of Harry Potter but I can see the appeal, see the value. I'm currently reading His Dark Materials - should I not because it was in the teenage section of Waterstones? They are bloody good books!
If you're as a discerning reader as you're making yourself out to be, and if you've read the books, you'd have picked up on the themes in it that are far from shit.