Vince Vaughn used to be funny. Or, more accurately, a surprisingly wide international audience used to find Vince Vaughn funny. The rambunctious persona premiered in Swingers – pure id in a party-hard alpha-male – then recycled in hit films such as Wedding Crashers and Dodgeball, made him a reliably lucrative booking. But last weekend saw his latest comedy – Unfinished Business, a farce about a work trip which gets out of hand – become the biggest flop of his career so far, with toxic reviews and audience apathy.

So far, so predictable: Vaughn’s recent back catalogue – Delivery Man, The Internship, The Watch and The Dilemma – have all crashed and burned at the box office. His last financial hit was the one-star Couples Retreat back in 2009 (AKA the film you almost watched on a plane that one time). So what went wrong? How did Vaughn go from being able to open a movie on the power of his name to being beaten by a film about S&M with no recognisable stars in its fourth week of release?

“Vince has just made some really unfortunate choices,” says Steven Gaydos, executive editor of Variety, “and I don’t think he’s got proper orientation around his strengths. He’s a terrific actor who had monster comedy hits, but he’s not a Will Ferrell – that is, a guy born to make us laugh.”

“Stars face a tough dilemma,” says box-office analyst Charles Gant. “Either keep churning out what worked in the past, or try something new. Vaughn seems to be doing the former, but who really wants to see a fish-out-of-water Euro-business-trip comedy starring Vaughn, Dave Franco and Tom Wilkinson? With Chris Pratt, Zac Efron and Robert De Niro it might have worked, but the premise is pretty unappealing.”

Will Ferrell and Kevin Hart in Get Hard. Photograph: Sportsphoto Ltd./Allstar

The trouble is: Vaughn is not alone. In 2004, the term “Frat Pack” was coined by USA Today to describe a group of actors who were then starring alongside each other in a string of hit comedies. Their films included Starsky & Hutch, Anchorman and Tropic Thunder and it seemed – for a while at least; a few halcyon days in the mid-noughties – that the whole world over was happy to lap up the Pack’s output.

Then the laughs dwindled and fans dissipated. Ben Stiller wisely chased those who now only went to the movies with their kids, with family-friendly franchises such as Madagascar and Night at the Museum. When he aimed his laughs at those nearer his own age (remember Tower Heist?) the response was much more muted. Jack Black’s appeal went south after Year One and The Big Year (note to Black’s agent: avoid titles with “year” in them), while Owen Wilson man-child comedies Hall Pass and Are You Here barely registered.

In the 11 years since the Frat Pack was christened, and the 18-odd since it formed, the climate of comedy has inevitably changed. The audience, also. The ever-crucial younger crowd, relied on by studios to come out in force on the increasingly-important opening weekend, have diminishing interest in watching men not far off 50 imitate children. Google-funded flop The Internship highlighted the Frat Packers’s misstep in this respect. Reuniting Wilson and Vaughn eight years after Wedding Crashers, the jokes – mainly of the “they’ve never even used a webcam before!” variety – served as an uncomfortable reminder of the divide between the stars on screen and the target demographic.

The need to age gracefully is acutely explored in Noah Baumbach’s comedy While We’re Young, out in the UK at the start of next month. It’s a reunion for the director and Stiller, who he took to dark (if financially unrewarding) heights in Greenberg; another film about the gap between being an adolescent imitating an adult and the terror of bill-paying, dream-burying responsibility. Stiller’s character in the new movie alternates between craving acceptance from his sophisticated elders and admiration from hipsters 20 years his junior. It’s a perfect fit for the star, almost uncomfortably so, and he delivers arguably his greatest performance.

Owen Wilson and Vince Vaughn in The Wedding Crashers. Allstar Collection/NEW LINE Photograph: Sportsphoto Ltd./Allstar

It certainly suits him better than his last attempt to “go straight”, 2013’s once-Oscar-tipped remake of The Secret Life of Walter Mitty. A pricey passion project for Stiller, who also directed, it confused fridge-magnet insight with profundity and wound up a pale imitation of fellow Frat Packer Will Ferrell’s underrated and under-watched 2006 comedy Stranger Than Fiction. But that inventive, whimsical tale of a man attempting to save his life from inevitability didn’t click with Ferrell’s core audience, despite strong reviews. The actor has made numerous attempts to break the mould, from Woody Allen’s Melinda and Melinda to Everything Must Go, an adaptation of a Raymond Carver short story. Yet such projects have never landed resoundingly, and he keeps scuttling back to more bankable ground. Plus, when it comes to opening tentpole releases, Ferrell is the obvious exception in the group, with solid returns for Anchorman 2 and The Campaign.

Yet despite this, Ferrell is increasingly unable to carry a comedy by himself. Later this month he teams up with Kevin Hart for Get Hard, playing a businessman preparing to enter prison. It’s a smart match, given that Hart’s fanbase – including 17.4m Twitter followers - has helped him score a string of recent hits. After that, Ferrell reunites with his Other Guys co-star Mark Wahlberg – a lone wolf outside the Pack, who manages to straddle comedy and drama – for Daddy’s Home (about a stepfather forced to compete with his wife’s ex-husband).

Ferrell’s continued chances to shine have, however, eluded Jack Black, who, bar the odd cameo, hasn’t headed up a film since 2011. His next lead is on the small screen, starring alongside Tim Robbins in The Brink, a comedy about a geopolitical crisis. Vaughn, too, has turned to HBO for salvation: the second season of hit crime show True Detective will see him play a career criminal alongside Colin Farrell (another actor in need of a hit). Speaking to Variety, Vaughn said he was “moving into a more adult part” of his career. Vaughn is 45 in a fortnight.

And Wilson too is having a rethink. Late last year we saw him in Paul Thomas Anderson’s Inherent Vice; soon he’ll be seen in his first non-comic part since 2001’s Behind Enemy Lines: an action lead in thriller No Escape.

As the Frat Pack disband, others plug the gap. “I think men behaving like idiots never really gets old,” says Gant. “We just need some fresh faces.” Judd Apatow alumni Jonah Hill and Seth Rogen scored the biggest lead role hits of their careers last year with 22 Jump Street and Bad Neighbours (both have sequels already in development). Melissa McCarthy used an Oscar-nominated role in surprise smash Bridesmaids to score three hits in a row; upcoming summer comedy Spy plus a role in the Ghostbusters reboot will test her status as the most consistently bankable comic actor working today.

The diversity that McCarthy and Hart represent (and even the nervy, chubby Hill and Rogen, too) suggest that part of the Pack’s key flaw today is its makeup: all white, all male, all of an age. Even their contemporary Apatow isn’t interested in making movies with them anymore. Instead he’s hunting for successors to Girls and producing and directing a vehicle for a relatively unknown woman (Trainwreck, starring Amy Schumer, positioned as one of the summer’s biggest).

And this, perhaps, is why the last gasp of the Pack – Zoolander 2, which Stiller and Wilson teased this week on the Valentino catwalk – may just be a stroke of genius. Derek and Hansel were aware they were ageing models ripe for the recycling bin in the first film. Fifteen years on, their plight mirrors that of the actors playing them. Maybe there’s pathos in going out of fashion.