I'm about three-quarters through, and I don't see that. It's going a pretty clear thematic point. Principally, documenting the minutae of middle class discontent and hypocrisy (which was something she also did in Harry Potter, albeit with considerably more whimsy), and criticizing the austerity regime of the current British government and the class attitudes behind it (which she's done openly before, as in the last British general election).
Some people are, in fact, "pretty damn stupid." Of course I was being a bit facetious there. However, authors are often thought of as a "brand": Stephen King is horror, John Grisham is legal thrillers, Louis L'Amour is westerns. Since Rowling doesn't have a "brand" beyond kids' books it wouldn't be surprising to have people automatically assume this book is for kids as well.
This is the second time I've noticed you proclaiming that Rowling isn't a good writer. Would you care to enlighten us as to why you think that?