“Tomorrowland” opens Friday at Point, Palace, Star Cinema and Sundance. PG, 2:10, two stars out of four.

Brad Bird’s “Tomorrowland” may be directly inspired by the Disneyland theme park, but it may be more emotionally connected to the name of a Scottish rock band called We Were Promised Jetpacks. Back in the optimistic prognostications of the 1964 World’s Fair (where “Tomorrowland” begis), the future was a bright and peaceful place, without war, hunger or ignorance. Now it’s 2015, and the future belongs to drone strikes, crumbling Antarctic ice shelves and selfie sticks. Where’s our friggin’ jetpacks?

In his wonderful Pixar films “The Incredibles” and “Ratatouille,” Bird explored the challenges of being The Best and Brightest in a world of mediocrity and greed. “Tomorrowland” continues that theme, extending it to the difficulties of being an optimist in a world of negativity, a world that desperately needs optimists. But it does so in a rather shrill and wobbly manner, making “Tomorrowland” a rare disappointment from Bird.

Young Frank Walker (Thomas Robinson) is the visitor to that 1964 World’s Fair, carrying his latest invention in a duffel bag. It is indeed a jetpack, although a malfunctioning one, and while the fair’s judge (Hugh Laurie) is unimpressed, Frank catches the eye of an enigmatic British girl (Raffey Cassidy). She gives him a pin, which, when he takes the “It’s A Small World” ride, unlocks a secret passage to a world of magic and enchantment. (Making him the only person who has actually enjoyed the “It’s A Small World” ride.)

Frank arrives in Tomorrowland, where the world’s Best and Brightest scientists, artists and thinkers have created a retro-futuristic paradise. They even fix his jetpack for him.

Then “Tomorrowland” takes an unexpected but satisfying narrative leap forward a half-century. Now we’re following another plucky dreamer, Florida teenager Casey (Britt Robertson). Casey lives in our world, one looking at a future far darker than Frank saw. Her father (Tim McGraw) is a mothballed NASA engineer now taking part in the dismantling of Cape Canaveral, a metaphor for our diminished dreams if there ever was one. There’s a montage of teachers preaching doom and gloom to Casey, who raises her hand and asks “But how can we fix it?” For her, optimism is a form of teenage rebellion.

Disney’s TOMORROWLAND..Casey (Britt Robertson) ..Ph: Film Frame..?Disney 2015

Casey also comes in possession of one of those little magical pins, which allows her to “see” into the Tomorrowland world virtual-reality style. This leads to the film’s one truly inspired comic setpiece, as Casey toggles back and forth between two worlds. Then that enigmatic British girl comes back around, egging on Casey to find Frank (now a bitter middle-aged man played by George Clooney) and figure out what went wrong with Tomorrowland’s present and our future.

“Tomorrowland” takes a while to reveal all its cards to us, which I enjoyed in a summer blockbuster season where the heroes and villains are quickly delineated. But it soon becomes clear that the film has less on its mind than it thinks it does; the storyline is constantly distracted by over-amped action scenes where Frank and Casey elude an army of turtlenecked robots on their tale. Instead of a slow build to wonder, we get scene after scene of things blowing up, robots getting heads and limbs severed, and innocent bystanders vaporized by death rays. It seems jarringly out of place in a PG movie, as if Bird and co-writer Damon Lindelof feared older kids would get bored otherwise.

The problem with tone extends to the characterizations — Casey and Frank seem relatively grounded for this kind of movie, but then there are characters like Laurie’s villain (later named Governor Nix — “Nix” as in “no”) and a pair of sci-fi memorabilia store owners played by Kathryn Hahn and Keegan Michael Key that are live-action cartoons. And when a film that’s supposed to be trying to do something different ends with yet another climax featuring a hero and a villain fighting as a doomsday machine clicks down to zero, it’s kind of depressing.

“Tomorrowland” has moments of genuine wonder, such as a jaw-dropping moment involving the Eiffel Tower, and its message — to look at the world’s problems with Casey’s “But can we fix it?” attitude — resonates. But the film is an imperfect, simplistic vehicle to deliver it, and what could have been a call to service ends up as “Turn your frown upside down!”