Pretty much everything I have to say about this film was said by Jim Emerson, already and better, here and here. I agree with every word he writes - except maybe I didn't like the good parts quite as much as he did.
So instead of trying to analyze this film myself, I'll just quote from Emerson:
The movie's adulterated sensibility is that of an alienated grown-up looking back at the (somewhat romanticized, over-intellectualized) misery of childhood and denying or downplaying the equally real fun stuff -- the in-the-moment joy, the exhilaration of being and imagining and doing and playing. So, in some sense it's a corrective to all those stupid "Isn't it wonderful being a kid?" movies that remember childhood through equally distorted rose-tinted lenses.... Especially the Wild Things, who aren't so much wild as the very opposite: neurotic, overgrown, overanalytical, dysfunctionally domesticated. They don't need a fake boy king, they cry out for group therapy. That's the source of my ambivalence about the movie as a whole: It's so transparently a narcissistic adult's diagnostic reinterpretation of childhood ("Will you keep out all the sadness?").And maybe part of the reason why the highs weren't as high for me, while the lows were just as low, is that childhood, preadolescence, isn't the part of my early life that haunts me: it's the teen years. I don't think about much at all that happened before I was about 13 - for better or for worse. High-school navelgazing I'm all over (need I say I'm hooked on Glee right now?), but childhood navelgazing doesn't resonate much for me. Dunno why.
But that aside, I am a narcissistic adult, so I'll tell you how this movie made me feel. Old. This movie felt like it was aimed at an audience of twenty-somethings, maybe just hitting thirty. The way the Wild Things talked, as well as the whole set of concerns, the anxiety about growing up and the vivid memories of childhood innocence, the sense that you can feel innocence slipping away from you by the second: all of that is the sensibility of someone not too many years out of college, I think. And I'm way past that, and this movie reminded me of it.
That's not a flaw in the movie, certainly. But the more I think about it, it is a peculiarity. I mean, I grew up on Maurice Sendak just like today's twenty-somethings did; more to the point, I was born within months of both Spike Jonze and Dave Eggers, who are responsible for this film. So why does their movie not speak to me? Why does it feel like it doesn't want to speak to my generation, but to the next one down? (If I was more familiar with Jonze's and/or Eggers' work, I might think there was an answer to that question; but I'm not sure.)
Maybe it's not actually old that the movie makes me feel, but alienated. Maybe this really is the voice of my generation, and I just don't speak that language. Maybe (gasp) I just don't fit in. Told ya high school was my favorite trauma ;)