Magic is the classic ingredient of the romantic comedy. Sleepless in Seattle makes it a whole theme. Behold Meg Ryan’s beautiful face, breathing the word out like she can manifest it into her life: “magic.” In What Women Want, it’s mind-reading. In Freaky Friday and 13 Going on 30, it’s body-swap. Then there’s the genre of romantic comedy that employs the wizardry of scripted life: The Holiday sends two women on vacation and waves a wand over their lives. You’ve Got Mail turns strangers passing in the street into soulmates. The greatest of this genre must be Moonstruck, a film in which no explicit spell is cast but instead, Shakespeare-like, Cher and Nicolas Cage’s beings bounce off one another into a perfectly choreographed future.

When magic structures a comedy it takes on two properties. First, it allows the writer to tweak the world into some different shape, allowing not only for bizarre hilarity, but an argument that it is only the structure of our lives that prevents us from understanding each other. Second, the magic infuses the world with a textural sense that things might be ordained or fated in a way that, outside the movie theatre, we only dare to imagine. Love is magic, movies are magic, and so a specific art form about the human heart arises.

I Feel Pretty promises this kind of twin enchantment. Renée (Amy Schumer) is a New York woman stuck in a tiny office underground, too insecure to pursue her dreams in love or in work. She stands before a mirror in her apartment in nude spanx and bra and her eyes filled with tears. One dark and stormy night she runs to the park and throws a penny into the fountain, wishing to be beautiful. Then one day at SoulCycle—one of far too many scenes that take place inside this brand—she falls off the bike and hits her head. While an employee (the very funny Sasheer Zamata) encourages this clumsy customer not to sue, Renée suddenly finds that her arms and legs are shockingly graceful. She looks in the mirror and marvels to find that her wish has come true.

Hi-jinks ensue. Renée now has the confidence to charmingly pick up a guy at a dry cleaner. Her work life transforms. Because a plot needs an arc, she also becomes something of a pill to her friends (the eerily tan Busy Phillips and the regular-skinned Aidy Bryant). Eventually she hits her head again and goes back to normal. Lessons have been learned. It’s okay to be ugly, is essentially the message of her final monologue. Just be confident.

There are a few authentically funny moments in the movie. Most of them are set pieces, as when Renée enters a Coney Island bikini contest and charms the crowd by declaring that “Renée is NOT afraid of returning things for store credit” while shaking her ass. At the movie’s end she tries to burst through a screen but instead just flings herself percussively against it like a pigeon on a plate glass window. There are also a few lines, seemingly improvised, that had the audience squawking. When an absurdly handsome work boss sidles into her bedroom, he has to flick Renée’s signature nude spanx out of the way. “That’s a bandage … for my leg,” she mutters.

The best comic performance comes not from Schumer but Michelle Williams as Avery, the beauty executive whose hamsterish voice holds her back in the workplace. She speaks like some five-year-old elf, but her behavior expands that sound into an extraordinarily funny embodiment. Avery leaps around like a faun in floral dresses, creepily bending to desk level and inclining her head blankly. It’s a terrific portrait of a woman trapped inside a creepy affect.

The premise of I Feel Pretty is promising. The idea is not Shallow Hal—it’s not in principle an exercise in making fun of women who don’t look like supermodels. But there are three problems in the movie’s execution that robbed it of the Moonstruck magic that every surreal romantic comedy aspires to. First, the script is dire. There seems to be a lot of improvisation in the film, as when Zamata has to keep a straight face while Renée acts like she’s Cindy Crawford. But otherwise there is zero Nora Ephron zing. I saw the movie in the kind of theater where people started dancing during the preview for Mamma Mia 2. We were so ready to laugh. Instead one of my friends kept leaning over to hiss objections, while the other fell asleep. The film wastes far too much time on workplace plot exposition and far too much time inside SoulCycle. There are simply not enough good jokes. A palpable chill drifted around the room.

Another big problem is that the magic of I Feel Pretty makes no sense. Why doesn’t she seek any medical attention for her several major head injuries? Why don’t her friends inform her that she still looks the same? If she’s so incredibly hot, why does she pursue a merely nice-looking guy, when it would have been so much funnier to see Renée cavort with some absurd beefcake? She’s also still diffident and anxious when faced with a very handsome man in her delusional period, which makes no sense. When the magic doesn’t work properly in technical terms, it doesn’t work in comedy terms. This world did not feel filled with the wonder of fate and chance and unlikely dreams come true.

The final problem is the one that has raged across social media in the wake of the movie’s trailer release. Amy Schumer is simply not an unattractive woman. There’s no makeover: from the movie’s start she wears nice outfits that show off her great legs. Her lustrous blonde hair bounces. Instead, the idea is, I suppose, that Renée’s self-image has nothing to do with the way she actually looks. It’s all about radical confidence, which will, alone, change your life. The big issue is that I Feel Pretty shows people consistently reacting to Renée as if she is hideous. The SoulCycle people humiliate her. Men ignore her. Receptionists don’t see her. Once she’s “hot,” it’s supposed to be hilarious that she enters the bikini contest and has such confidence. There’s no sense at all that these reactions are the product of her anxiety alone. This person is not hot, the movie’s world says, which structurally undercuts the psychological journey its protagonist is supposed to complete.

The trailer backlash was perhaps unfair, since the movie truly could have been good. Schumer is a big ball of problems, but she is undeniably funny. Her career is in the waiting-room of redemption. In what should have been a major breakthrough for this comedian, I Feel Pretty instead becomes a good idea totally hamstrung, gutted, eviscerated by poor writing. A spell without sparkle is no spell at all. By the end you’d rather be concussed yourself.