Isaac Hayes wasn’t completely kidding in 1971 when he said this cat Shaft was a bad - well, you know the rest. Hayes’ theme song was a bit of a sendup, but the movie, “Shaft,” was not. Richard Roundtree played John Shaft, a black private eye whose tough reputation preceded him even among the white cops of New York City.

Shaft became an icon among black audiences (and beyond) for his street-smarts, swagger and anti-authority attitude.

Samuel L. Jackson plays another version of the character in the new “Shaft.”

You’re as likely to find this guy drinking in nightclubs as delivering a beatdown.

He still packs heat and loves a good fight, but his main concern now is solving a murder case alongside his estranged son, JJ (Jesse T. Usher), a by-the-book FBI agent.

That’s right — “Shaft” is not just an action-comedy; it’s a family comedy (though with an R rating).

Directed by Tim Story (“Think Like a Man”) and written by Kenya Barris (creator of ABC’s “Black-ish”) and Alex Barnow, “Shaft” tries to find humor in the clash between generations — Shaft, the macho dinosaur, and JJ, the respectful-to-a-fault millennial — while also doling out gunfights and car chases. It’s an attempt to modernize the five-film franchise, give it a friendly spin and establish a crowd-pleasing blueprint for future episodes.

It may succeed, but at a cost.

Despite the dependable charisma of Jackson (his second time in the role, after John Singleton’s 2000 version), the character of Shaft has utterly lost his edge.

Shaft has become one of those disreputable dads who nevertheless has some hard-knock wisdom for his pampered son. That set-up might work if the jokes felt more contemporary (do people still say “metrosexual?”) and if JJ’s character wasn’t such an emasculated cliché. Also, for all the talk about what makes a man, the film takes a dim view of women. Regina Hall plays the reductive role of Shaft’s nagging ex-wife, Maya, while Alexandra Shipp plays JJ’s crush, Sasha. During a shootout, Sasha pulls out a gun, only to have JJ grab it away and make himself the hero. Her reaction: panting arousal.

The film stages a climactic gunbattle featuring Shaft, JJ and Granduncle Shaft (Roundtree, actually just six years older than his nephew Jackson), but by then we’re not much in the mood for action. All told, this is one soft “Shaft.”