Rampage bA big slice of “meh” dumped into the no man’s land between “Ready Player One” and a certain high-profile Marvel movie, “Rampage” is an afterthought that barely qualifies as a distraction for those waiting for the summer blockbuster season to kick off in earnest.

To be fair, it’s not that it’s bad per se, just mind-numbingly mediocre, and a bit of a letdown after seeing star Dwayne Johnson mine a similar vein like a pro in “Jumaji: Welcome to the Jungle” just a few months ago. Hell, how can the Rock swagger through cheesefests like the “Fast & Furious” movies, “San Andreas,” and “Baywatch” yet seem totally adrift here?

It should have been a no-brainer: The movie is based on a late-’80s arcade game spawned by the creature-feature films of the ’50s and ’60s, in which one to three players controlled giant monsters as they stomped the bejeezus out of one cityscape after another while the tiny cartoon populace reacted accordingly. Add a plot, and it’s movie.

Which of course is easier said than done, especially when it comes top video game movies. In this instance, Johnson plays Davis Okoye, a primatologist whose best friend is an albino gorilla named George (mo-capped by Jason Liles), residing at a San Diego facility.

Enter one of three canisters of green gas that fall to earth from a disastrous experiment by sleazy corporation Energyne, run by cartoonishly arch Claire Wyden (Malin Akerman) and her dimwit brother Brett (Jake Lacy). The gas turns the genial George super-aggressive and begins to increase his size considerably; it has an even more pronounced effect on a wolf in Wyoming and an alligator in the Everglades.

After that, things get frustrating for the bulk of the movie’s middle section, with plenty of wheel-spinning and pointless banter to kill the time between a couple of so-so action sequences, one of which kills off an intriguing supporting character five minutes after he’s introduced.

We’re stuck watching the villains play to the rafters, and the Rock’s bland romance with a crusading scientist (Naomie Harris, Oscar nominee for her performance in “Moonlight”) until the titular orgy of mass destruction finally rolls around; sadly, it’s hamstrung by sketchy CGI. Fortunately, George is there to still some of the spotlight, as is Jeffrey Dean Morgan (“The Walking Dead”) as a CIA agent with cowboy affectations and an “eh, screw it” attitude. It’s too bad they’re not the main characters.

Tellingly, there’s a moment in the film when George flips Johnson the bird; by the time it’s over, the audience may want to do the same.