It’s probably safe to presume that, had he known the political climate into which he would be dropping his debut English-language film, the legendary Chinese director Zhang Yimou would have chosen a subject other than the heroism of warriors defending an immense national wall against an invasion of horrifying aliens. But, to paraphrase Donald Rumsfeld, you go to the cineplex with the army you have.

The Great Wall, a Chinese-American co-production starring Matt Damon as a European mercenary fighting (literal) monsters during the Song dynasty, could have been a marvel. Zhang has directed sophisticated dramas (Ju Dou, Raise High the Red Lantern) and thrilling action pictures (Hero, House of Flying Daggers). The cast includes talented American actors in Willem Dafoe and Pedro Pascal (who was magnificent as Oberyn Martell on Game of Thrones); and Chinese stars both relatively new (Jing Tian) and firmly established (the great Andy Lau). And as a general rule, Damon is as reliably excellent a lead actor as you’ll find anywhere in Hollywood.

Alas, rather than multiply these talents productively, The Great Wall reduces them to their lowest common denominator. It’s not a terrible movie, exactly. (For one thing it’s too short to be, clocking in at a merciful 104 minutes in an era when CGI epics frequently approach twice that.) But it’s certainly not a good one.

Damon plays William, a rogue who makes the perilous journey to China in search of “black powder,” a fabled substance that can “turn air into fire.” The others in his mercenary band are all killed en route, save for Tovar (Pascal), who with William discovers an unimaginably vast wall garrisoned by selfless warriors called the “Nameless Order.” Their mission, he learns, is to protect China against the Tao Tei, hideous quadrupeds with eyeballs in their shoulder blades. (Envision a pitbull as reimagined by H.R. Giger, and you won’t be far off.) These toothy creatures hurl themselves at the wall by the thousands every 60 years, like really, really ornery cicadas.

As in the past—even in his second-tier films such as Curse of the Golden Flower—Zhang’s palette is a chromatic marvel. The defensive forces are resplendent in brightly laminated armor that would not be out of place in Marvel’s Asgard: black for foot-soldiers; red for archers; and, best of all, an all-female cadre of “crane warriors” led by Lin Mae (Jing), who take lances in hand and hurl themselves down from the high parapets like bungee-jumping amazons. There are conspicuous echoes of movies as varied as Lord of the Rings, Starship Troopers, How to Train Your Dragon, and Mulan.

Alas, Zhang’s moments of visual splendor—a battalion of hot-air balloonists, the queen-monster and her royal guard of fan-frilled monstrosities—are weighed down by a script and performances almost dutiful in their dullness. Virtually every plot development is telegraphed in advance, and to call the supporting characters two-dimensional would be to insult planar surfaces.

Perhaps the greatest disappointment is Damon, who for the first time in memory seems to have absolutely no idea what he’s doing onscreen. His character is meant to be Irish, but I would never have guessed it from his accent, which sounds like the flattened-out grumble that one occasionally gets when British actors try to play Americans. Memo to Zhang: If you’re looking for “generic white action hero” go the Pacific Rim/Godzilla route and hire Charlie Hunnam/Aaron Taylor-Johnson. (Or was it the other way around? Who among us can confidently recall?)

Indeed, Pacific Rim and Godzilla are in some ways forbears to Zhang’s disappointing film. There was a brief, misplaced controversy over whether Damon’s casting was an example of “whitewashing” akin to Tilda Swinton’s portrayal of the Tibetan “Ancient One” in Doctor Strange. It isn’t: Zhang always intended a Western actor for the role in order to broaden the film’s appeal beyond Asia. Instead, The Great Wall is a disheartening reminder (like Pacific Rim, Godzilla, the last Transformers movie, and other recent Hollywood product) of the dangers of aggressively tailoring a film to a “global audience.”

The difference, of course, is that in this case the tailoring is principally coming from a novel direction: an Asian filmmaker trying to make it big in the American market, rather than the other way around. Nonetheless, the result is comparable: dialogue, motivations, and characterizations are simplified in order to defy cultural misinterpretation—but as a result also lack any meaningful resonance or connection. And they are all in the thrall of a relentless parade of explosions and CGI effects that translate the same way into every language.

Indeed, what is most interesting about The Great Wall, apart from is its occasionally brilliant visuals, are the explicitly Zhangian elements that still remain, in both aesthetics—this could not be mistaken for an American movie—and ethos. (The theme of obeying orders for the greater good, taken to a fault in his previous works, is present in less ominous form here.) Zhang’s film is still unlikely to make much of a dent in the U.S. box office. It’s a pity that he seems to have so intently compromised his artistic vision in a misplaced effort to do just that.