I have a few problems with “Rogue One.” My biggest problem has nothing to do with the film itself, but its very existence. The idea of “Star Wars" branching standalone efforts that do not mix into the Skywalker saga is admittedly intriguing, but I feel that it somewhat hinders the sacredness of George Lucas’ galactic opera. Part of what makes the “Star Wars” films so treasured is that there are only so many of them. Now, we’re going to get a new film every year, even after the sequel trilogy ends. Just how many of these spin-offs Disney and Lucasfilm will pump out remains to be seen. (Honestly, does there have to be a Boba Fett movie?)

All that aside, “Rogue One” begins this new slew of series offshoots with a technical prowess that ranks among the best in the franchise. Battle sequences, both on the ground and in the stars, are some of the most handsomely mounted pieces of blockbuster spectacle this year. We have no one but Gareth Edwards (the sharp-eyed director of 2014’s “Godzilla”) to thank for just how great this film looks. It’s just a pity that the actual drama and the characters caught in the middle of it feel sadly underwhelming. There’s a more-than-welcome diversity among the main players of Edward’s film, but what a shame it is to see their full potential go to waste.

Four years after the rise of the Galactic Empire in “Episode III - Revenge of the Sith,” research scientist Galen Erso (Mads Mikkelsen) is forcibly recruited by Imperial advanced weapons director Orson Krennic (Ben Mendelsohn) to finish his work on the planet-evaporating space station dubbed The Death Star. His daughter, Jyn (Felicity Jones), is consequently adopted by Clone Wars veteran Saw Gerrera (Forest Whitaker). Fifteen years later, some time before the events of “Episode IV - A New Hope,” Jyn is recruited by Rebel intelligence officer Cassian Andor (Diego Luna) to help find her father so that the Rebellion may know how to eliminate the Empire’s new technological terror. The duo is aided by K-2SO (Alan Tudyk), a reprogrammed Imperial enforcer droid, Bodhi Rook (Riz Ahmed), a former Imperial pilot, blind warrior Chirrut Imwe (Donnie Yen), and his mercenary companion, Baze Malbus (Jiang Wen).

These are all fascinating names for characters that don’t quite live up to their collective coolness. Everyone in “Rogue One” has at least one moment to shine, and those moments are fairly amusing. Chirrut and K-2SO are by far the most outstanding, as Yen charismatically shows off his martial arts skills, while Tudyk masters the droid’s comedic timing. Even so, the script seems curiously uninterested in fleshing each member of this unlikely team beyond the clever one-liners and zingers crafted to coerce average viewers into rooting for them. Not even Jyn - though written better than the others, and played exceptionally by Jones - can win the viewer over in the short amount of time it takes to set all the pieces on the board before the climactic action rolls around. (Is every parentless girl with a British accent in “Star Wars” from now own going to be a self-sufficient, hard-edged loner who grows through the power of companionship?) At least the prequels, weakly written as they are, tried to devote a little more time to their characters.

More sweat is dedicated to the expansion of the “Star Wars” universe, as Edwards and his team behind the camera populate the galaxy far far away with new planets to be explored. Production design is as strong as ever, and Edwards knows exactly how to photograph it. Scenes are under-lit to enhance the gritty, war-torn atmosphere, plus Edwards has a great deal of fun with the sheer scale of the effort (as he did with “Godzilla”). AT-ATs actually look like the towering terrestrial terrors they were meant to be in “Episode V - The Empire Strikes Back,” while crumbling landmasses obliterated by the Death Star make spaceships look like insects caught in a rocky tidal wave. There is some familiarity to the film’s aesthetic, but never has it been so intensely grounded, not even in the original trilogy. If only Edwards had more freedom to push the grit even further instead of needing to secure fanboy delight with franchise easter eggs.

Too often does “Rogue One” edge closer to the dark war film it should be, only to push itself further into the realm of fan service. One reason for this is the replacement of composer Alexandre Desplat with Michael Giacchino, who is practically the closest thing we have to John Williams right now. I might have savored the gritty tone a bit more if Giacchino wasn’t trying to live up to his potential as Williams’ successor. The most frustrating result of the film’s derivativeness is when it reveals itself as nothing more than filler for a plot hole in “A New Hope,” though this reveal is smartly handled by the writers. I would estimate that about half of “Rogue One” is devoted to characters, images and other small references to the original film in order to make fans squeal with joy, although I would certainly be lying if I told you I wasn’t at all fazed by the scenes where Darth Vader appears. Unsurprisingly, the dark lord gets the film’s two best scenes, although one of them - as cool as it is - feels a bit tacked on and obvious. Other familiar faces are resurrected through the magic of CGI, but because they are so clearly CGI, they take you right out of the movie.

It has many ups and many downs, but “Rogue One” is nevertheless a fun side story for “Star Wars” lovers to devour and debate endlessly. Perhaps future spin-offs will stray further from saga continuity and take more narrative risks, but this seems unlikely, because until the sequel trilogy is complete, these offshoots will serve as pleasant little time killers for those who cannot wait for installments in the primary canon. The Force is with this one, albeit not so strongly.