The tone of “Expend4bles” can be summarized in a single close-up: a corpse’s severed hand flipping the bird. To its director, Scott Waugh, and all those responsible for resurrecting this dormant action franchise, the middle finger gestures toward this fourth installment’s intended style: macho, smirky and defiant. At its best, the film is all three. This all-star mercenary squadron composed of ’80s-to-aughts brutes is the cinematic equivalent to Slash’s Snakepit, a supergroup throwback to an era when men were meatheads and we in the audience merrily cheered them on.

I’ll admit I still did, at least for some of this swaggering inanity. Why resist the impossible physics of Curtis Jackson (better known as 50 Cent) body-slamming a baddie back and forth like a toddler throwing a temper tantrum with his dolly? Or Dolph Lundgren lampooning his aging vision by screwing a prescription lens onto his sniper rifle? Or Sylvester Stallone grumbling about a thumb-wrestling injury that he’s chosen to nurse with a tiny custom leather sling? Or Jason Statham, the comically gifted bruiser now promoted to the series’ lead, doing, well, pretty much anything?

In an even earlier era, Statham’s nimble skills would have awarded him a career like Jimmy Cagney’s. But he’s stuck working in ours, with a script that offers a few enjoyable quips — he calls an enemy “a sneaky little sausage” — but mostly lets him down. The screenwriters Kurt Wimmer, Tad Daggerhart and Max Adams seem to share a mutual disinterest in the plot, intoning the words “detonator” and “World War 3” until the threats become background static.

These high jinks would be more fun if the actors didn’t look so unflappable. Nothing breaks their composure. Not explosions or blood spatters, not beheadings or nuclear bombs, not even the sight of a warship careening in the Sea of Japan. (Perhaps because all of the above have been cheaply rendered in post.) Even a back-flipping, insult-slinging seduction scene between Statham and a new teammate, played by Megan Fox, climaxes without a lip-gloss smudge. It’s just one more artificial palpitation.

The energy sputters along on throwaway gags, like when Jacob Scipio, as a motor-mouthed young Expendable, sips a cocktail with a pink umbrella at a wake. There’s an absurdly enjoyable detour with a lecherous internet influencer (Samuel Black) and a shootout interrupted by a stereo blasting 50 Cent’s “P.I.M.P.,” which is just plain absurd. Is Jackson the rapper in the same universe as Jackson the assassin? Does he moonlight in carnage?

Andy Garcia, Randy Couture, Levy Tran and the great martial artist Tony Jaa round out our cast of protagonists while Iko Uwais heads up a generic goon squad, giving all the intensity he can to a villain written with no identifiable traits other than a scar. When things get dull, there’s always Lundgren in the background, playing up his character’s nearsightedness with the daffy charm of Marilyn Monroe. But the film’s last reel is so awful — so sneeringly contemptuous of our good-faith efforts to play along with these shenanigans — that we leave the theater still thinking of that middle finger. It sure seemed pointed at us.