It sounded like the dream team. On one hand you had the exceedingly likeable Amy Schumer, who, in a relatively short period of time, has become something of a comedy superstar—her sketch TV show Inside Amy Schumer, with its distinctive post-feminist tone and irreverent, hilarious skewering of contemporary sexual and gender mores, has rightly placed her among America’s most in-vogue comics of late. And on the other, there was Judd Apatow, the Lord of the Bromance himself, who has had a hand in some of Hollywood’s most successful comedy films and small-screen projects including Freaks and Geeks, Anchorman, The 40-Year-Old Virgin, Superbad, Bridesmaids, and, more recently, Lena Dunham’s Girls. A collaboration between these two—in the form of a film written by and starring Schumer and directed by Apatow—spells fireworks, you’d have thought. But although the new Trainwreck does flicker and flare pleasantly every now and then, particularly when it manages to channel Schumer’s raw, biting wit, it’s overall a lot tamer and a lot less funny than you’d expect, pretending to be on a mission to annihilate the rom-com formula before quietly succumbing to it—a sheep in wolf’s clothing if there ever was one.

The film’s prologue features a father (Colin Quinn) teaching his two little girls how “monogamy isn’t realistic” as a means of justifying his having stepped out on their mother—and the consequent divorce. Twenty-three years later, while one of the daughters (Brie Larson) appears to have tossed that maxim straight out the window, the other, Amy (Schumer), seems to have internalised it big time. Amy has been living it up in New York for a while now: she’s a hard-drinking partier who has more one-night (or half-night) stands than she can count—we watch her emerging from one strange bed after another, ready to hotfoot it out the door soon as the sex is over, before the guy decides he wants to talk, or worse, *shudder* cuddle. Her job, at a high-end men’s magazine, is only helping perpetuate this lifestyle: the publication, called S’Nuff, is headed by the petrifyingly angular Diana (Tilda Swinton, totally unrecognisable) and packed with titles such as “You’re Not Gay, She’s Boring”.

While it’s easy to stay with the story so far, what happens next comprises the sort of fully-unlikely-in-real-life contrivance that rom-coms are littered with: Amy, despite professing an utter lack of interest in sports, is assigned to write a story on sports doctor to the stars Aaron Conners (Bill Hader). And wouldn’t you know it, Amy and Aaron turn out to be complete opposites (shocking, I know), and as such, they’re bound to attract—their first date ends like most of Amy’s dates, in bed. Strange thing is, the very next day, when she’s made her requisite getaway, he seems to want to see her again, and again, and yet again. Will Amy allow herself to ditch those commitment-phobic ways and actually consider settling down? Or will the self-destructive streak she’s inherited from her father mean she’ll screw this up like all the other relationships in her life? The answer, my friend, is the obvious one.

The most effective bits in Trainwreck are the ones that feel like skits taken straight from Schumer’s TV series, where she’s known to call out the preposterousness of sexism and gender stereotypes with such refreshing, self-effacing, unapologetic candour that even the least prude among us will feel the occasional blush coming on. And, importantly, she doesn’t sacrifice comedy for commentary—the woman is seriously funny. Case in point: Schumer’s Twelve Angry Men sketch, one of her best parodies so far.

That kind of subversive energy is certainly apparent in the first half of Trainwreck—our protagonist, for instance, displays the sort of traits usually attributed to the overgrown man-children running wild and shunning adulthood in Apatow’s world, not to mention the fact that she is a ways from the perky, size-zero leading lady who is usually cast in such films. Amy here, much like the Amy from the TV show, is a foul-mouthed, superficial, selfish, boozy jerk—just “not nice”, as a guy tells her at one point—the sort of female character that we never used to see on screen until not too long ago. But though her life might look messy, she seems very much in the drivers’ seat, having chosen a path that she’s happy to go on treading—in heels yet—sans shame.

That is until the movie veers suddenly onto the beaten track when it decides that the only thing to be done with such women is to tame them by way of starry-eyed romance. Apatow’s influence becomes startlingly clear in the film’s dull second half where the laughs peter out and we’re subjected to the very conventions of romantic comedies that the film was expected to upturn; it’s a strange, hard-to-swallow cop-out, especially given Schumer’s penchant for punching through propriety. For all the freedom that it affords her in the beginning, Trainwreck ultimately does the main character a disservice by proclaiming a tidy, monogamous union as the only means of salvation. Amy’s partying and sleeping around are things that need to be corrected—this isn’t what women should want; it’s a sad moment where the viewer can’t help but catch the whiff of compromise coming off this supposedly semi-autobiographical project. By the time the ridiculously happy ending rolls around, the disillusionment will have become too much to bear.

Thank goodness, then, for a solid cast, the film’s sole saving grace. Although her character is a tad underdeveloped—as are the others—Schumer is watchable as ever, her childish features lending impact to the filthy lines coming out of her mouth. Hader, meanwhile, serves up a nicely understated performance as the straight man here, a deviation from the sort of eccentric stuff we’ve seen him do on Saturday Night Live and in other film stints over the years. And in a movie packed with celebrity cameos—some of which feel utterly unnecessary and merely a drag on the already-lengthy running time—it’s wrestler John Cena and NBA star LeBron James who make the most memorable impressions, the latter proving especially hilarious in a role that puts the support in ‘supporting actor’.

Despite getting off to a promising start, then, Trainwreck slowly fizzles out as it goes on, never quite able to rise above rom-com constricts. Of course, it might be a little unfair to expect Schumer to constantly push a feminist agenda in every project, every joke, but for someone being hailed by many as placed to take over the female comic mantle from the likes of Tina Fey and Amy Poehler, making the sort of concessions one has reason to suspect she has in this particular film feels like a couple hundred steps backward. Still, I remain a Schumer fan, and very much hope that she’ll be back on form the next time around.