“It’s a kid’s game,” one character utters early in Gangster Squad. How telling, that throwaway line, about this purely cartoony concoction, which aspires to ape only the pretty fashions of L.A. Confidential and none of its pulpy ferocity or feeling.

That’s because director Ruben Fleischer and screenwriter Will Beall treat this 1950s story about the Los Angeles Police Department’s secret gang assembled to muscle out East Coast mobster Mickey Cohen like kids playing dress-up. They stuff the film with fetishistic slo-mo effects, charmless violence and thin characterization for which a passel of Oscar winners or nominees can’t compensate.

While it’s a step up for Fleischer from the dismally dim 30 Minutes or Less, it seems evident his brilliant feature-film debut, Zombieland, was a screenwriter’s triumph all the way, and that he’s a stylist only as good as the script he’s given. With Beall, that’s one goofy gimcrack (“I don’t need a hero, Sarge. I need a husband.”) after another.

The hardheaded husband in question is Sgt. John O’Mara (Josh Brolin), assigned to handpick a group of vigilantes for an off-the-books assault on the empire of Mickey Cohen (Sean Penn).

Playing the heavy, the Oscar-winning actor recycles his nasal “tawk” from Sweet and Lowdown and resembles Robert De Niro by way of Dick Tracy. The creased latex lines of Penn’s makeup seem visible throughout, either from laughing, or frowning, at lame dialogue he’s asked to shout. Penn likes to sling grief at contemporaries like Johnny Depp for making what he calls “monkey-fuck-rat” movies. Penn’s purely paycheck performance here brings another hyphenated phrase to mind: “pot-kettle-black.”

Tasked to take Cohen down are Sgt. Jerry Wooters (Ryan Gosling), a gadabout who turns into the Terminator after the death of his favorite shoeshine boy; Officer Coleman Harris (Anthony Mackie), a patrolman singlehandedly pushing down Cohen’s heroin trade in his neighborhood; Officer Max Kennard (Robert Patrick), a True Detective hero in the Old West gunslinger mode; Kennard’s cohort, Officer Navidad Ramirez (Michael Peña); and surveillance expert Officer Conwell Keeler (Giovanni Ribisi).

As if attempting to distinguish this clearly lesser work or just goofing on the whole endeavor, Gosling affects a squeaky voice a la Boardwalk Empire’s Mickey Doyle. He also fails to rekindle a believable romantic spark with Emma Stone, which salvaged the so-so soapiness of Crazy, Stupid, Love. Here, she plays Grace Faraday, arm candy to Cohen whom Wooters woos away, much to the squad’s endangerment.

Of this large cast, only Mireille Enos rises above as O’Mara’s long-suffering, pregnant wife, who knows that if she can’t talk her man out of his crusade, she’ll select his cohorts.

Many of its action scenes are awkwardly augmented with CGI, especially an opening duke-out in an elevator and a car chase that carries a mid-’90s halo of cheapness. The film is best when it finds some unexpectedly appropriate humor in how the squad’s gung-ho, guns-blazing approach backfires, namely in an early Burbank raid.

The rest is rife with remnants of what could’ve been more engrossing in the hands of a director who didn’t fawn over slow-motion Christmas ornament explosions — the violent unmooring of World War II veterans asked to assimilate back into civil society, the idea that for Cohen to be humbled under the magnesium flash of the media’s cameras stung more than any arrest, the barely tickled underbelly of L.A.

Although it’s blunt and brisk in its own inoffensive way, Gangster Squad is meathead cinema — the sort that cuts hard from a splattered brain to spatula-pressed hamburger. Unlike that grilled patty, Gangster Squad is mostly sizzle, no steak.

At least Gangster Squad’s Blu-ray presentation captures all the technical vavoom it has on its side. Its visual transfer handles the seductive reds and inky blacks of Dion Beebe’s cinematography, showcases the slimmest fibers on Mary Zophres’s costumes, and outlines the immaculate period detail of Maher Ahmad’s production design.

The DTS-HD MA 5.1 surround track blasts its buckshot across the sound field, too, but never at the expense of dialogue fidelity even at the film’s most thunderous moments.

Extras include: standard-issue commentary with Fleischer; seven deleted scenes (none of which is the now-infamous theater-shooting scene — featured in early trailers but edited out in a release date-delaying move after the July 2012 Aurora, Colorado, shootings); the Gangland Files picture-in-picture experience with trivia snippets, interviews and more; a total of 16 behind-the-scenes featurettes; photographic comparisons of the film’s locations then and now; and a documentary profile of the real Cohen, narrated by William Devane.