There are plenty of “I’ll be back” in-jokes in “Terminator: Dark Fate,” the latest entry in the cyborg-on-a-mission film series, but the most obvious one is missing: “I’ll be bad!” Because “Dark Fate” be really, really bad.

Sure, it’s nice to see 63-year-old Linda Hamilton, returning to the role of Sarah Connor for the first time since 1991’s “T2: Judgment Day.” But nostalgia alone doesn’t cut it. In fact, giving us happy memories of the first two films — some of the best of their genre — is what hurts this impostor the most.

Like last year’s “Halloween,” which similarly saw the comeback of a more mature Jamie Lee Curtis, “Dark Fate” pretends much of its series never happened. That’s OK here, because the succeeding iterations since “T2,” starting with 2003’s “Rise of the Machines,” were defective.

This one begins on a beach in Guatemala. Utilizing the most de rigueur of tech gimmicks, we witness a de-aged Hamilton and a digitized young Edward Furlong as her kid, John Connor. Then, the T-800 (Arnold Schwarzenegger) materializes in front of them and kills the little guy.

What that means is that Sarah’s plot to destroy all of the evil Skynet’s technology and prevent mankind’s destruction has failed, and that the eventual leader of the resistance, John, is dunzo. Back to the drawing board! This is nothing more than the filmmakers’ wiping the slate clean for what’s sure to be a slew of subpar sequels.

In the present day, two visitors from the future arrive via time travel from the year 2042: a Terminator Rev-9 model (a well-cast Gabriel Luna) and Grace (Mackenzie Davis). The target this time around is Daniella, played with determined blandness by Natalia Reyes, and there’s a feeling of déjà vu. The Terminator even rips off Arnie’s famous line. “I’m looking for Daniella Ramos,” he tells a neighbor. “I’m a friend of hers.”

Grace, we learn, is an “augment,” or a human with some RAM and a battery. She has been sent to protect Dani, who’s vital to the human resistance of the future. Grace can kick ass, but she’s also pretty boring. When her big mystery is revealed, it elicits a shrug. Sarah, now a full-time Terminator hunter, meets up with the duo on a highway and tags along for the destruction.

The villainous company has been re-dubbed Legion. With all the word swapping, this movie often comes off as a dystopian game of Mad Libs.

As blissfully simple as James Cameron’s original “Terminator” framework was, “Dark Fate” has a tendency to toss in unnecessary confusions. For example, Schwarzenegger’s T-800 is now in his 70s — how does skin glued to a metal skeleton age? — and has become Carl, the father figure for a boy and mother he rescued. “She needs my help … with the groceries,” he says. The family, however, is oddly unconcerned that he does not eat said groceries.

The “Terminator” action, by and large, has always been made up of realistic highway car chases, violent shootouts and a bit of hand-to-hand combat. But director Tim Miller has gone overboard with special effects here, staging an impossible fight on an airplane, which leads to a cheap-looking underwater sequence. Whenever Arnold kicks and punches, he swiftly flies through the air — less of a hulk than a prima ballerina.

But it’s Dani and Grace who really fry this circuit board. Back in 1991, there was a gravitas to Hamilton, and even to 14-year-old Furlong, that made us believe the pair could save an imperiled world. Reyes and Davis can’t even save their movie.