It’s telling that two of Rampage’s big set pieces end with a gigantic albino gorilla laughing and giving the finger straight into the camera. It’s certainly the most apt representation of the viewing experience for this Dwayne Johnson–starring creature feature, an epic disaster movie that sees a mutated gorilla, crocodile, and wolf tear apart downtown Chicago. I went in looking for some good cheap fun in line with Johnson’s last blockbuster, Jumanji: Welcome to the Jungle—maybe a mix of expensive-looking action and jokes at the expense of Johnson’s super-sized muscles. Instead, I got an ape flipping the bird.

Rampage faces the same essential problem so many disaster movies do. It’s an entirely ridiculous film, churning out piles of CGI city-smashing carnage only for the audience’s enjoyment. But it’s also trying at all times to maintain a serious, highly macho vibe straight out of an ’80s Schwarzenegger movie, framing Johnson as an invincible hero who alone can save the day. It’s a mismatch that only gets worse as things go along. The director Brad Peyton (who worked with Johnson on Journey 2 and San Andreas) switches between shots of giant animals gleefully burrowing into the Willis Tower and brave first responders rescuing civilians. Any moment of real danger gets punctuated with gags like a gorilla’s middle finger. It’s an icky combo.

Perhaps a tonal clash was inevitable in a film with four credited writers, one that’s based on an ’80s arcade cabinet that consisted wholly of animals destroying skyscrapers. Once Rampage tries to weave in plot and characterization, the experiment becomes untenable. But if you’re interested in watching some CGI creatures cause chaos while Johnson peppers in comments like, “Well, that’s not good!” then Rampage might do the trick.

How did the albino gorilla (his name is George) get so big? Well, Rampage opens with a title card laying out the banned scientific practice of “genetic editing” (essentially, the rewriting of DNA), then cuts to a space station being terrorized by a rat the size of a tiger. This vessel belongs to a corporation called Energyne, which has been carrying on the banned research for nefarious purposes. But when an animal subject rebels, the whole shebang explodes into Earth’s atmosphere, dropping poisonous DNA canisters into a swamp (next to a croc), a prairie (by a wolf), and yes, into the gorilla enclosure at the San Diego Zoo.

That’s where George lives and hangs out with Davis Okoye (Johnson), a loving primatologist who carries on conversations with the ape (performed in motion capture by Jason Liles) in sign language all day. Unfortunately, once George gets a whiff of the noxious space junk, he starts growing exponentially larger and is filled with an unquenchable desire to (stick with me here) … rampage. In Chicago, namely, the home of the evil corporation that infected him. It’s up to Davis, former Energyne employee Kate Caldwell (Naomie Harris), and a government agent named Harvey Russell (Jeffrey Dean Morgan) to stop him.

And stop him they don’t—after all, the movie needs to live up to its title. Instead, George and the other two monsters menace the city as Davis and company race around looking for a cure. The bond between Davis and George could have made for a slightly different kind of monster movie. But once George is weaponized, his personality disappears, and the audience instead has to be invested in a hunt for a hidden serum Kate developed called a “chill pill.”

The movie takes great pains to convince the audience of Davis’s competence, even though he’s powerless to stop George. Johnson’s character is an ex-soldier, a man who can bash any skull in front of him, pilot any vehicle, and fire any weapon. But none of that is useful in this situation, so the film shoehorns in a bunch of fight scenes. In Jumanji: Welcome to the Jungle (which was actually set inside a video game), Johnson had fun playing a digital avatar, mocking his own absurd proportions and litany of super-abilities. Rampage takes that exaggerated persona at face value, rather than cleverly undercutting it.

Of the ensemble, Morgan is having the most fun by giving his government agent character a Foghorn Leghorn accent and a heaping scoop of Texas swagger. As the corporate villains, Malin Akerman and Jake Lacy are as cartoonish as possible, trying to play to the back of the theater (she’s mean; he’s stupid), but the particulars of their wicked plan never make enough sense. The real antagonists, of course, are the monsters. But since they’re being piloted against their will by a genetic gas, it’s hard to get too worked up over them, even as Chicago skyscrapers topple like logs. George can roar (and gesture rudely) as much as he wants, but Rampage is a big, noisy nothing—an action extravaganza that fails at being funny just as hard as it fails at being serious.