“If you’re not a genius, don’t bother,” the English professor played by Mark Walhberg in “The Gambler” blithely tells his students. That should be one clue that you’re not gonna like this guy.

But there’s a bigger problem with that line, because it inadvertently makes us think: If you’re not doing a genius remake of an old movie, why bother? Director Rupert Wyatt’s new version of the 1974 drama that starred James Caan as a self-destructive gambler lacks the bite and heft of the first. It also largely wastes an excellent cast.

At the center is Wahlberg, a talented and appealing actor who is either miscast or misguided here. As Jim Bennett, a professor with a dangerous addiction to gambling, he’s cool, slick, handsome — and that’s pretty much it. We never once understand the three most important things about him: why he’s drawn to teaching, why he’s drawn to gambling, and why he’s so pitifully prone to self-destruction.

Moreover, we don’t understand why people keep giving this infuriating character another chance — like his mother (an excellent Jessica Lange), a woman whose pursed lips, icy veneer and dark glasses hide a heart than still cares for this wayward son.

Or like Amy (Brie Larson), the thoughtful student in Jim’s class, who watches him leap through the lecture hall like a swaggering talk show host, telling students they’ll never amount to anything — except her. Amy, he says, is the only one with enough talent to write. Somehow she accepts this claptrap (which frankly borders on teacher misconduct, though we digress) and decides Jim’s a catch.

We first meet Jim as his grandfather, a wealthy banking magnate, is on his deathbed. The old man informs Jim he won’t be leaving him a dime. He’s on his own.

Next thing we see, Jim’s at a high-end gambling den in a mansion overlooking the Pacific (Wyatt and screenwriter William Monahan have moved the setting to Los Angeles from the New York) where Amy works as a waitress. It’s clear that Jim doesn’t know when to stop. At blackjack, he’ll win, and win again, and then bet it all — until he loses.

Soon he’s in debt to the tune of a couple hundred grand to the owner, Mister Lee (Alvin Ing.) Sinking deeper into the quicksand, he accepts $50,000 from another loan shark, Neville (Michael Kenneth Williams of “The Wire,” highly entertaining). Now he owes two people.

It’s up to Mom to bail out her son, and she tries, albeit reluctantly. Jim isn’t even grateful. With poor Amy watching (this is indeed a thankless role, both for Amy and for Larson) Jim loses it all again. Seems he doesn’t like being helped.

As Amy says: “You’re one of those guys who started out with no problems at all, and now you have all of them.”

The movie’s other good lines pretty much all go to John Goodman, who livens up the proceedings each time he appears. Goodman plays Frank, another loan shark, this one an amateur philosopher. One moment he’s a genial adviser, giving a perfectly rational explanation of how owning a home and saving a little money will protect anyone against life’s ups and downs. At another, he’s scary as hell, telling Jim that if he borrows and doesn’t pay back, Frank will methodically erase his entire bloodline.

Somehow, Jim will have to figure out how to save himself, and it’ll be more complicated than borrowing from Peter to play Paul. The ending — a departure from the original, again — is satisfyingly creative and suspenseful.

By then, though, it feels too late. We didn’t really care enough about Jim to be invested in his ultimate fate. They sorta lost us at hello.