Djimon Hounsou as Bedivere and Charlie Hunnam as Arthur in “King Arthur: Legend of the Sword.” (Daniel Smith/Warner Bros. Pictures)

This piece discusses the plot of “King Arthur: Legend of the Sword,” which … I don’t even know anymore, you guys.

“King Arthur: Legend of the Sword” has battle elephants, fashy haircuts, David Beckham and Rodents of Unusual Size. What this messy, impoverished take on Arthurian legend from director Guy Ritchie doesn’t have is a basic semblance of cinematic competence, ideas it wants to express or even an obvious rationale for being. It’s the worst movie I’ve seen in theaters since “Batman v. Superman: Dawn of Justice.”

Even before we arrive at the substance of “King Arthur: Legend of the Sword,” the movie is one of the most impressively incompetent aspiring blockbusters I’ve ever seen. The editing, by James Herbert, often renders much of what’s happening onscreen completely incomprehensible. The soundtrack drones and screams; grafting Arthurian legend and metal together doesn’t exactly elevate the latter (there’s also a certain amount of exaggerated manly shrieking, too). The extensive and ill-executed use of CGI to achieve an exhausting and unnecessary level of spectacle ends up making the movie feel cheap rather than overwhelming. At a moment when video games are scaling new heights of visual and narrative ambition, the tacky magical cosplay the film’s antagonist assumes upends the pop culture hierarchy. “King Arthur: Legend of the Sword” isn’t proof of film’s dominance; it’s a movie desperately straining to be a video game.

These deficiencies wouldn’t have merely sunk a movie with a sharper plot and stronger characters: They would have buried it at the bottom of the ocean. “King Arthur: Legend of the Sword” is not a movie with either, however.

Act Four contributor Sonny Bunch described Charlie Hunnam’s riff on this English founding myth as “chav King Arthur,” which is basically correct. By circumstances too convoluted to recount, this Arthur ends up not being fostered in the home of a minor noble, but growing up in a Londinium brothel and running a variety of scams on the side. Once his destiny arrives, Hunnam spends a lot of time squinting, scowling, resisting said destiny, getting knocked out by his magic sword and hollering in the mud. (Jude Law does his own unfortunate share of emoting as the evil usurper Vortigern; it says a great deal about the movie that his very bad performance is not the most memorably awful part of the movie.)

He’s surrounded by a collection of characters who made me suspect that Ritchie is either actively trolling advocates of a more diverse Hollywood, or accidentally making an argument that we should abandon the effort, lest we wake unintentional horrors. Djimon Hounsou plays a knight of high and rather dull rectitude named Bedivere. Tim Wu is George, the proprietor of a Londinium kung-fu academy, because that’s a thing. Aidan Gillen is in the mix, too, as an ace archer and a representative of the community of people whose accents sound fake, no matter which one they’re doing at any given moment.

And these half-baked sketches are scattered through a movie that is not remotely sensible. By the end of it, I couldn’t figure out why Ritchie had wanted to tell a King Arthur story at all.

He’s not sufficiently interested in the tension between paganism and Christianity to have attempted a “Mists of Avalon”-style revisionist take on the Arthurian legend. Here, Mordred (Rob Knighton) is a generic Bad Sorcerer with hordes inelegantly swiped from “Lord of the Rings” and who challenges Arthur’s father, Uther (Eric Bana), rather than a relative of Arthur’s who perpetrates an intimate, searing betrayal.

The women of Arthurian legend, including his wife, Guinevere, his half-sister Morgan la Fey and his aunt, Morgause, are absent, too. Astrid Bergès-Frisbey’s character doesn’t even get a name: She’s just the Mage, seemingly the last remaining member of England’s magical community. Women in “King Arthur: Legend of the Sword” pretty much only show up to be sacrificed to snake-like things, or to conjure up said serpents. In addition to the snakes and that magic sword, the movie has a bunch of significant towers: This is not a subtle piece of cinema, though it is a relatively sexless one.

And although there is a castle that’s called Camelot, and at the end of the whole affair, a table that is circular in shape, it mostly feels as if Ritchie wanted an excuse to throw his signature style of smart-hooligan dialogue, frenetic chase scenes, a large special effects budget and a new setting into a blender. “King Arthur: Legend of the Sword” would make more sense if I’d known that Ritchie had thrown darts at a bulletin board with a lot of different mythical traditions on it and come up with this one. As much as “Batman v. Superman” often made choices that felt inexplicable, and executed them in a way that I found ridiculous, I at least understood why Zack Snyder wanted to tell stories about Superman, and his perspective on the character.

Trash can be fun. “King Arthur: Legend of the Sword” is dreary garbage.