Few movie series reboots have enjoyed immense box office success and critical acclaim in the way that the current James Bond iteration has.

This is not without warrant; “Casino Royale” (2006) portrayed Bond in a refreshingly vulnerable and human way, “Quantum of Solace” (2008), while less substantive, managed to hold up the space between fantastic bookends, and “Skyfall” (2012) is the gorgeous, logical culmination of everything these modern Bond films have done right.

“Skyfall” director Sam Mendes is at the helm again, which should have offered more opportunity for complexity and continuity across multiple films that may not have been possible with the three different directors we’ve had so far.

So with all this going for it, what happened to “Spectre”?

At the outset, it’s honestly hard to say. A promising opening sequence tracks Bond through the crowded streets of Mexico City, costumed to blend in with the tens of thousands of costumed individuals celebrating the Day of the Dead.

The entire sequence is expertly orchestrated, plenty tense, and overall gorgeous in color and detail. Every moving part contributes to the sense of festivity and danger.

Meanwhile, Bond (Daniel Craig) gets to be simultaneously charming and intimidating throughout the scene, which is more or less his modus operandi.

Then things start exploding, buildings start collapsing, and helicopters start flying upside-down…somehow. Alright, sure, this is a James Bond film – there’s bound to be plenty of this stuff, and in this scene, it fits as the climax to the tension that’s been built up.

But that’s just it: The opening sequence builds up to the popcorn action in a way that totally works – and a way that’s never again seen for the rest of the film.

What made “Casino Royale” unique was its ability to be, undeniably, a Bond film, while mixing style and subtlety. What made “Skyfall” brilliant was its ability to balance emotion and action – Bond’s human side and his propensity for being where things explode.

Where “Spectre” fails is in leaving all of this behind, as the stunts and action sequences are almost nonstop. They become increasingly ridiculous to the point where Bond, from a moving boat, is quite literally shooting down a helicopter at long range with the last bullet of a pistol.

Let that one sink in for a second.

All humanity is not lost from Bond in this movie, but it’s exponentially more forced than it has been thus far in the series. Bond’s family drama was handled well in “Skyfall,” and it was an important contributor to his character; Bond’s family drama hits soap-opera tier in “Spectre.”

In a similar vein, “Spectre” has the problem of having some excellent turns by great actors playing characters who are woefully underdeveloped.

Daniel Craig is as charismatic as ever as Bond, and it’s becoming increasingly apparent that he will come to rival Sean Connery as one of the favorite Bonds of all time – if never truly surpassing the original.

His opposite and primary antagonist, Ernst Stavro Blofield, is portrayed by Christoph Waltz, and this was a big selling point of the movie for me.

But where Bond has had three films (and most of a fourth) to gain complexity of character, Blofield has essentially had none, and he’s not fully in the film until there’s maybe a third left to go.

The result is a Bond villain that, for the first time in this reboot, is actually the stereotypical “Bond villain,” with all the cat-owning tropes that moniker brings.

Late in the film, we’re shown the true nature of Blofield’s influence on the series to this point, which I suppose is a bit too spoilery to discuss, but it’s an underwhelming revelation. Besides that, Blofield’s motivation is fairly ridiculous and ham-fisted.

This lack of development is fine for characters like, say, Q (Ben Whishaw), whose dry humor as Bond’s quartermaster is welcome and generally necessary. It just doesn’t work for a character that’s supposed to be held up as Bond’s true equal.

As a film taken independently of what came before it, “Spectre” is a decent entry into the Bond franchise. But as the follow-up to some of the best 007 films we’ve seen since GoldenEye in 1995 – two decades ago – it’s a disappointment. Mr. Mendes, we know you can do better.

“Spectre,” rated PG-13, is still playing in theaters. Like my reviews? Have a disagreement? Give me a shout on Twitter at @MovieMuseSean.