This is not Lewis Carroll's Alice in Wonderland, nor is it Disney's. It's dark, a bit dystopian, quasi-surrealist, very Tim Burton in a lot of ways. But who is it for?
The visuals, set design, setpieces, and acting are teen to adult—only certain kids will take these in without being troubled or having nightmares.
On the other hand, the plot is incredibly, incredibly simple and not subtly revealed. It amounts to: girl (Alice) doesn't like her life because everyone tells her what to do. Girl flees to wonderland, where everyone but her thinks she's a hero. After some initial resistance, girl accepts that she's a hero and slays dragon (jabberwock). This gives girl the confidence to return to her real life and tell everyone bossing her around to shut up.
This is not a plot synopsis, this is effectively the plot—not very much happens other than that. Flee to wonderland. "You're a hero." "No I'm not." "Yes you are." "Okay, I guess I'll try." Dragon gets slain. "I did it!" Return to real life with knowledge she's a dragon-slayer. "Shut up, all of you!" The end.
The stuff that takes up the time is mostly just conversation and little bits of fiddling about—sight gags and Burtonesque visuals and so on. Absolutely a kid-only plot in terms of sophistication and sustained interest. There's just not enough meat here—no intrigue, no character relationships, nothing in particular—to keep an adult interested.
So we have a movie that has a kid-style plot—enough to fill a picture-book of about 20-25 pages with a girl-and-dragon morality play fairy tale. Yet we have adult visuals—giant heads and grotesque people and severed heads and fingers and so on.
Basically, it's the Tim Burton logic taken to the extreme—take a kid-level idea and roll it up into deeply adult visuals.
Who is this for? I suppose at the end of the day, there is a segment of kids that will enjoy it. They're the kids that aren't squeamish and love surreal and troubling stuff. They do exist.
Of course, kid #1 in this group is Tim Burton himself—who is probably the person this film is really for!