Midway through “Vacation,” the intrepid Griswold clan unwittingly takes a dip in a lake filled with human excrement, which is roughly how most viewers will feel after enduring 90-odd minutes of this miserably unfunny, mean-spirited and just plain wrong reboot of the much-loved 1980s and ’90s National Lampoon comedy series. Corralling a new generation of family members for another ill-fated trek toward that theme-park mecca known as Walley World, this new “Vacation” leans heavily on franchise nostalgia — with multiple cover versions of Lindsay Buckingham’s “Holiday Road” theme song and token cameos for original stars Chevy Chase and Beverly D’Angelo — but trades the earlier films’ endearing buffoonery for a cheap nastiness reminiscent of writers (and first-time directors) Jonathan Goldstein and John Francis Daley’s “Horrible Bosses.” A trip to the corner store with this cast of characters would be an endurance test — which, with any luck, is as far as the movie’s box office returns will carry it.

When he penned the script for the first “Vacation” (based on his National Lampoon short story “Vacation ‘58”), the late John Hughes was riffing on his own memories of tumultuous family excursions in smoke-filled station wagons, and of a suburban middle-class America that aspired to the gleaming perfection of the families in department-store Sunday circulars. Consisting of bickering but loving teenage siblings Rusty and Audrey, impossibly patient mom Ellen, and quixotic dad Clark (whose best-laid plans inevitably curdled), the Griswolds were like a live-action Flintstones or Simpsons (avant la lettre), and the good will of the first movie carried over into three lesser but enjoyable sequels (the best of which, 1989’s “Christmas Vacation,” has since become a December perennial). But the Griswolds of the new “Vacation” really are the family from the Sunday circulars: They seem to have met each other at a casting call a few minutes before the cameras rolled, and the movie itself doesn’t seem to like them very much.

One good measure of what’s off about Goldstein and Daley’s approach comes right in the opening scene, when the now-adult Rusty (Ed Helms), a pilot for a discount commuter airline, takes an in-flight bathroom break, leaving the plane in the hands of a senile co-pilot — a gag that would feel gag-worthy even if it didn’t arrive with the Germanwings disaster still making headlines. Another indicator comes a bit later, when Goldstein and Daley give Rusty his own version of the first “Vacation’s” encounter between Clark and a Ferrari-driving babe (Christie Brinkley then, Hannah Davis now) — a scene, in the new movie, whose punchline is a violent head-on collision.

Like the summer’s other tentpole movie set inside a fictional theme park, “Vacation” shows us that it understands the burden of expectations that come with resurrecting an iconic franchise. “We’re not redoing anything. This will be completely different,” an exasperated Rusty assures his sons, pint-sized bully Kevin (Steele Stebbins) and sensitive, guitar-strumming James (Skyler Gisondo), in the course of explaining why he’s decided to retrace the very route his own parents took to Walley World once upon a time. Unpersuaded, the kids respond that they’ve “never even heard of the original vacation.” (A more direct nod to “Jurassic World” comes in the form of Walley World’s newest and most popular roller coaster: the Velociraptor.) From there, “Vacation” proceeds as a scattershot mix of homage (a temperamental minivan known as the Tartan Prancer — “the Honda of Albania” — in place of the immortal Wagon Queen Family Truckster) and the sort of self-congratulatory vulgarity that seems to have spewed forth from the (junior high) locker room instead of the writers room.

The Griswolds have endured a lot over the decades, though this “Vacation” is the first one where they’ve been road-raged by a pedophile truck driver and nearly taken over the falls by a suicidal river-rafting guide (Charlie Day). That generally depressive air is only compounded by watching so many gifted performers struggling to prop up such flaccid material (including no shortage of dick jokes, gay jokes, gender-identity jokes). The always game Christina Applegate, such a spry comedienne in the “Anchorman” pics, is utterly wasted here as Rusty’s long-suffering missus, on hand mainly to projectile-vomit her way through a round of drunken sorority games during a visit to her Memphis alma mater. Still, she escapes with slightly more dignity than does Chris Hemsworth, on hand mainly to prance about in his skivvies as the vain Texas TV weatherman who’s married Audrey (a similarly underused Leslie Mann). Least of all are Chase (looking frightfully bloated) and D’Angelo (looking radiant at 63), whose 11th-hour appearances seem tacked on as a post-production afterthought.

Key to the success of the “Vacation” movies was their underlying sweetness — the sense that, for all their foibles, the Griswolds were a surprisingly functional lot. Families looked up at the screen and saw a version of themselves reflected back. Look at the new “Vacation” and all that stares back is a great comic void.