While slogging through the new crime film “The Alto Knights” this week, a depressing thought came up.

Has Father Time put a hit on Mafia movies?

The limping genre’s best stars and directors are all in their 80s. Its New York stories, once bracing and violent, feel exhausted, like they’re contemplating a move to Boca Raton.

And fans, not gung-ho for the new ones, are content to just re-watch and quote the classics.

Robert De Niro stars in “Alto Knights” — a movie that the Post called dense, unfocused and confusing.

Back in the day, seismic films like Francis Ford Coppola’s “The Godfather” in 1972 were able to masterfully bridge prestige (the Oscar for Best Picture) and mainstream taste ($250 million at the box office; $711 million when adjusted for inflation).

“Knights” is projected to bomb with a nothing $3 million this weekend. And if we somehow see it at the Academy Awards next March, that means everybody’s gone on strike again.

“Knights” stars — who else? — 81-year-old Robert De Niro as both Frank Costello and Vito Genovese of the Luciano crime family (later to be known as the Genovese crime family). The actor is so identified with Mafioso parts they didn’t even bother giving him a co-star. He actually talks to himself in scenes.

Francis Ford Coppola’s “The Godfather” in 1972 won the Oscar for Best Picture and made $250 million at the box office, which is $711 million when adjusted for inflation. Courtesy Everett Collection

The movie itself, written by “Goodfellas” (De Niro, Joe Pesci) and “Casino” (De Niro, Al Pacino) scribe Nicholas Pileggi, 92, is terrible; a not-so-greatest hits collection of mob cliches.

Most gangster films these days are. The last exceptional one (and some of you might take exception to this) was 2019’s “The Irishman” starring — who else? — De Niro, Pacino and Pesci.

Yet in order to plop those stalwart actors in a plot that spans decades, director Martin Scorsese, 82, had to use CGI to de-age them back to their 20s.

Christopher Serrone, Robert De Niro, Joe D’Onofrio, in “Goodfellas.” ©Warner Bros/Courtesy Everett Collection

2019’s “The Irishman” starred De Niro and Pacino, which to Oleksinski is “the last exceptional one.” AP

In 1990, “Goodfellas” had a different person play young Henry Hill before the late Ray Liotta took over for the rest of the run time. And De Niro himself starred as a spry Vito Corleone in “The Godfather Part II” after Marlon Brando was so brilliant as the older version of the Don.

Perhaps Scorsese went the “Avatar” route because, in the past, the technology wasn’t available to give marquee names digital facelifts. But I think there’s more to it than a software update.

The truth is, the further away we get from the heyday of the Italian mafia, the less performers look like believable wiseguys.

When De Niro, Pacino and Pesci are no longer with us, who is going to take these Sunday spaghetti and bullet-in-the-head roles? Timothée Chalamet?

Ray Romano, Al Pacino, Robert De Niro, in “The Irishman.”

Many have embarrassed themselves trying.

Over the past decade we’ve been whacked by “Gotti,” the turkey starring a freakish John Travolta, and “Capone,” the, er, capon with mumbly Tom Hardy. Both fowl. Audiences felt let down by the “Sopranos” prequel “The Many Saints of Newark” featuring Alessandro Nivola as Tony Soprano’s uncle.

The genuine Tony, James Gandolfini, who died in 2013, could have been the big-screen exception, but we’ll never know.

“Over the past decade we’ve been whacked by “Gotti,” the turkey starring a freakish John Travolta,” Oleksinski says. Everett Collection / Everett Col

Look, mob movies have had a good run, and these shifts happen. Westerns were an American cinematic fixture until the 1960s and ‘70s. Then audience’s tastes changed, and now when one pops up it’s a darker, modern spin like “The Hateful Eight” by Quentin Tarantino.

That’s the best we can hope for, really. That an innovative young director and an exciting screenwriter with a hankering to tear up the Mafia flick playbook will come along, look at all the beloved films that came before them and say, “Fuggedaboudit!”