Steven Spielberg has a lot to answer for. That’s the chief thought that went through my mind while watching “Jurassic World Dominion,” the sixth and final installment —  or so we’re told — of the franchise that began almost 20 years ago with “Jurassic Park.”

Mr. Spielberg didn’t direct the current film. That credit goes to Colin Trevorrow, one of many contemporary filmmakers blessed with an inordinate amount of technical skill and whose pictures evince not a scintilla of vision. He’s a movie machine. 

Mr. Trevorrow also helmed a previous entry in the series — “Jurassic World.” He co-wrote that film, as well as “Jurassic World: Fallen Kingdom.” Did they turn profits on their umpteen-million-dollar budgets? You might as well ask if the Giganotosaurus was the largest carnivore that ever walked the planet.

This fact is explained several times over during “Jurassic World Dominion,” in bits of dialogue clearly stitched onto the working script. How important is the paleontological record to a run of films that are, basically, variations on “Frankenstein”? Ask any teenage boy who grew up parsing the distinctions between the brachiosaurus and the brontosaurus, and you’ll get an earful.

This brings us back to Mr. Spielberg — the world’s most successful teenage boy — a director who helped to codify the perpetual adolescence typical of Hollywood products. He’s the executive producer of “Jurassic World Dominion.” 

Mr. Spielberg has done good work, of course. His revamp of “West Side Story” was an improvement on the 1961 original, and “The Adventures of Tintin” is an unsung masterpiece. Mr. Spielberg has proved capable of difficult ventures, “Schindler’s List,” “Amistad,” and “Munich” among them. Box office clout allows for such gambles.

Yet Mr. Spielberg’s first and best blockbuster, “Jaws,” was the beginning of the end for a Hollywood that catered to, you know, grown-ups. Mr. Spielberg isn’t the only guilty party. George Lucas and John Landis, as well as a host of related talents, accomplished something that had previously been unthinkable: the elevation of B-movie tropes into A-movie status.

With the outrageous success of films like “Jaws,” “Star Wars,” “Raiders of the Lost Ark,” and “An American Werewolf in London,” subjects that had previously been consigned to the local grindhouse or the drive-in movie circuit were rubber-stamped as profit-takers and encouraged by the front office. The marginal, in other words, went mainstream. 

All of which resulted in the climate through which we’re all persevering, one in which superheroes, aliens of one-stripe-or-another, and over-size, extinct reptiles dominate the multiplex. If you’re not able to tap into your inner adolescent nowadays — well, good luck to you.

How satisfied audiences will be with “Jurassic Park Dominion” turns out to be a good question. Eavesdropping on the crowded house in which I saw the movie offered a lesson in the law of diminishing expectations. Not a few members exited the theater bemoaning the blatant iteration of previous set pieces. A nearby set of Gen Z-ers made no bones about the relief they felt about the film “finally” ending.

“Jurassic Park Dominion” clocks in just short of three hours, presumably because a lot of loose ends needed to be tied up. You see, the stars of the original “Jurassic Park” —Laura Dern, Jeff Goldblum, and Sam Neill — meet up with Chris Pratt, Bryce Dallas Howard, and Isabella Sermon, the actors who have been in the more recent films.

They encounter each other on the grounds of Biosyn Genetics, a corporation run by Dr. Lewis Dodgson (Campbell Scott), who is, as you might expect, up to no good. Not only is he responsible for a plague of oversize crickets wreaking havoc on the world’s agricultural supply, but he has the temerity to hire Soyona Santos (Dichen Lachman), a fashion-forward operative who specializes in smuggling dinosaurs.

Would that the bad guys had won, if only because Mr. Scott and Ms. Lachman fill out their roles with consummate panache. As for the good guys: They’re window-dressing around which a lot of nifty dinosaurs thunder, galumph, and skitter. Mr. Goldblum gets off some tart zingers, but, then, he always does. 

What we’re left with is an adventure that culminates with the lion laying down with the lamb, the triceratops commingling with the elephant, and the characters played by Ms. Dern and Mr. Neill getting busy. Suffuse this denouement in a golden halo of light reminiscent of nothing so much as a Hallmark greeting card, and you have the overstuffed descent into juvenalia that is “Jurassic World Dominion.”

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Correction: Colin Trevorrow directed a previous entry in the series, “Jurassic World.” He co-wrote that film as well as “Jurassic World: Fallen Kingdom.” An earlier edition of this article misstated his directing and writing credits.