In its setup, "Tomorrowland" invites audiences to imagine a world where the greatest innovators, artists and scientists of the past 120-some years weren't inhibited by the constraints of politics, distraction, greed and presumably budget. Imagine all the wonders they would create.

Directed by Brad Bird, who has brought audiences such poignant and grand blockbusters as "Ratatouille," "The Incredibles" and "Mission: Impossible - Ghost Protocol," you'd expect "Tomorrowland" to pay off on this promise, delivering an awe-inspiring epic full of spectacle and emotion. Instead, we get a tedious adventure, more preachy than powerful.

Part of the problem is a story that doesn't make much sense. Maybe you've watched the trailers and wondered, "But what's it all about?" I've seen the movie, and I still struggle to answer that. But here goes:

Casey Newton (radiant ingénue Britt Robertson) is a plucky optimist who dreams of a future full of space travel and incredible advancements for humanity. However, her present is full of naysayers -- that is until she gets a mysterious pin that throws her temporarily into the titular alternate dimension. Desperate to go there, she seeks out Tomorrowland ex-pat Frank Walker (George Clooney as an action grandpa) and teams with Athena (Raffey Cassidy), a whip-smart robot who looks like a little girl and fights like a superhero, to save the world from its own negativity. This lumbers into a conclusion that is apparently happy (the music tells us so), but profoundly confusing.

The script from Bird and "Lost's" Damon Lindelof reads like a 12-year-old's TED Talk, packed with good intentions, but light on substance. Characters repeatedly state the theme in phrases best suited to motivational posters, like "It's hard to have ideas, and easy to give up," "You can fix the world," "We are the future" and "Just be yourself!"

Beyond that, there's little faith that this movie created for kids will make much sense to them. (It won't, judging from the many adults it confused when I saw it.) So, plot points are repeatedly rehashed by a confounded Casey asking what's happening. Aside from being annoying and unhelpful, this also undercuts the heroine's reported reputation for being smart enough to save the world, when she can't fathom just about anything that's occurring along the way.

However, the script's greatest fault is that it sets up a story that should be full of action, adventure and spectacle, but fails to live out that screenwriter edict, "Show don't tell." Characters talk, talk, talk instead of doing much, including actually spending much time in Tomorrowland. The movie doesn't really feel like it starts moving until we get there, and that doesn't happen until late into the second act.

There are a handful of action sequences, with some fun elements, including guest appearances by comedians Kathryn Hahn and Keegan-Michael Key, who should just be in all things. But the stakes of these setups are killed by a bookend device that shows you from the first frames that your heroes are safe and sound. Beyond that, the CGI employed is of that slightly too slick variety that makes people look like they're made of rubber instead of flesh. Considering this is a big Disney summer movie, I expected much more than CGI on the level of "Harry Potter"s sloppiest Quidditch scenes. Actually, I expected much more on every level.

I wanted to like this movie. Because of Bird, I expected to love it, as his previous films are some of my all-time favorites. ("Iron Giant" represent!) There are moments of promise, like an early section where Athena and Casey seem to be in an all-girls "Terminator" spinoff, complete with dizzying fight choreography, zippy one-liners and some genuinely horrifying violence. But all in all, "Tomorrowland" is a massive letdown. Lacking in visual storytelling, emotional resonance and spectacle, it doesn't feel like a Brad Bird movie at all.

To the credits of its stars, they are charismatic even when delivering mind-numbing dialogue. But their combined charm isn't enough to save this movie from ponderous rhetorical somersaults.

"Tomorrowland" opens Friday nationwide.