In a New York Times article published yesterday, Maria Tatar suggests that the often frightening fantasies of today give kids and young adults less space to play in wonderlands than did their counterparts in earlier decades and centuries. I agree with some of the points she makes, though I'm not sure that scary books necessarily give readers more of "a dose of adult reality" than cheerful books do. Yes, scenes of violence and political unrest may reflect realities or project possibilities, but so do scenes of love and triumph, regardless of one's age. I don't think the question is one of adult reality, but rather one of story structure and how it's changing. A home-away-home pattern was once pretty standard for kids' books, particularly those for middle-graders and younger. That pattern hasn't disappeared, but my sense (anecdotally) is that it's appearing in fewer stories now.
(A few non-shocking spoilers below.)
It went without saying in the 1860s that Alice would make it back up the rabbit hole. Small, happy-ending changes were standard, but they might be as slight as a bell under a Christmas tree and a happy memory of a Polar Express train. But things change irrevocably for Harry Potter and for a lot of his young descendants (I speak not of the painfully named Albus Severus). It's especially true in YA, but the middle-grade world is hardly immune.
I'm not calling the change a good or a bad thing. Characters should change and grow. In many cases lately, particularly in dystopian fiction, their worlds change and grow with them, which is awesomely empowering for the characters and thus for the readers. But I think there's value in both types of structures. There's great comfort in a home-away-home story, and I hope that comfort, like Max's supper, is still hot.