Note to readers: Mild spoilers ahead.

George Lucas, the genius behind the first six “Star Wars” movies, says that his films are defined by “a sort of effervescent giddiness.” That’s true, and it’s central to their magic.

That helps explain why writer-director Rian Johnson’s new film, “Star Wars: The Last Jedi,” isn’t really “Star Wars.” Sure, it’s good, even very good – but there’s nothing giddy about it.

Lucas’ films bristle with contagious delight in their own audacity. Have a look at the opening scenes of the very first “Star Wars” film, later named “A New Hope,” when the massive Star Destroyer appears on the screen. Shown from below, it goes on and on, and on, and on again and then some more. It’s a joke. Back in 1977, audiences laughed; some of them stood and applauded.

Although Star Wars is a bit of a cartoon, it also has feeling and depth, and real insight into human psychology. Drawing on Joseph Campbell’s idea of “The Hero With a Thousand Faces,” Lucas told a universal tale (actually, two tales) about heroic journeys and freedom of choice, exercised for better or for worse by two young men, Anakin Skywalker and his son Luke. Both of them are deeply tempted by evil. Lucas is candid and vivid about the seductive, even erotic power of the Dark Side of the Force.

Anakin is seduced; he becomes Darth Vader. Luke is barely able to resist – and for a crucial moment, he too is seduced. Lucas’ story, reflecting the influence of Christianity (and the hope in every human heart), offers a lesson: All of us can be redeemed if we choose the Light when the chips are down.

When Lucas’ protagonists do go bad, it is for one reason: They cannot bear to lose someone they love. The path to the Dark Side is paved by grief and loss. But in a stunning reversal of what seems to be his main theme, Lucas also shows that fear of loss (otherwise known as love) is the path to redemption as well.

At its heart, Lucas’ tale is about fathers and sons, and about how much they need each other. Luke believes – whatever the objective evidence – that his father has good in him. (Doesn’t every son believe that?) Vader gives his life to save his son. (Wouldn’t every father do that?)

Having studied the topic with care, Lucas is also insightful (and enduringly relevant, above all in the much-maligned prequels) about how democracy falls and how authoritarianism rises. He captures the populist allure of the all-powerful leader. As one of his characters puts it, “So this is how liberty dies … with thunderous applause.”

Anakin Skywalker himself insists, “We need a system where the politicians sit down and discuss the problems, agree what’s in the best interests of all the people, and then do it.” Ominously, he adds that if they refuse, “They should be made to” – and if that sounds like dictatorship, “Well, if it works …”

“The Last Jedi” has a lot to say about the Light Side and the Dark Side, but there is nothing about grief and loss, and it’s banal about democracy. What it does with good and evil isn’t nearly interesting enough. Rey, our heroine, is never truly tempted. That’s boring.

Mr. Dark Side, Kylo Ren, does have a bit of a struggle, and in that sense, Johnson maintains continuity with Lucas’ vision. But in this movie, at least, the struggle turns out to be a head fake. Because Kylo’s descent doesn’t have the precipitating cause of Anakin’s – the loss of loved ones – and because we don’t see Kylo suppressing the better angels of his nature, the film doesn’t come anywhere close to the depths of Lucas’ films.

The script flags the idea of freedom of choice, but it’s not heartfelt – more like checking a box. In that sense, and worst of all, Johnson ends up losing Lucas’ golden thread.

Many people have criticized “The Force Awakens,” which rebooted the series in 2015, as a recapitulation of Lucas’ early work. Fair enough. But at least it was crisp and tight, it left plenty of open questions, and it offered some giddiness of its own.

“The Last Jedi” doesn’t. It’s a self-conscious passing-of-the-guard, told with nostalgia and a whiff of tragedy. Too much of the time, it lacks exuberance.

True, Mark Hamill is fabulous as the old Luke Skywalker, and as Rey, Daisy Ridley matches him. Johnson’s work is more than competent; it’s sharp and inventive (and in a few places, stunning). But it doesn’t wrestle with demons or with the largest questions. It isn’t brimming with life.

It’s a reminder that George Lucas was, and remains, one of a kind.