The film claims it is expressly for all the "girl dads" out there. Having now seen it, that much is true: despite its family-friendly brief, IF is less for kids than for the adults of kids – the girl dads, if you will – who want something that feels a little more mature than Minions but doesn't scare the kids away. Far from it; it might just bore them to tears.

It's a bold shift for Krasinski, who's already transitioned from sitcom lead to successful director with the Quiet Place series, and yet, looking at the man himself, it makes perfect sense. He's the kind of all-American aw-shucks new dad who dipped his toe into the horror genre, and now wants to make a fun movie that his children can watch.

The results, such as they are, play out like a half-baked live-action adaptation of a Pixar picture, from the Monsters, Inc-like structure of the IF world and the dramedic coming-of-age tales of Inside Out and Up.

Bea (Cailey Fleming), stays with her equally effervescent grandmother (Fiona Shaw, one of the film's highlights) at her old, creaky apartment building. It's while there that she suddenly develops the ability to see people's imaginary friends (or IFs, as the film so proudly dubs them), and gets looped into an adventure involving her grandmother's downstairs neighbor, the cynical IF whisperer Calvin (Ryan Reynolds). You see, he's been running a kind of matchmaking service for IFs whose kids have stopped believing in them; once they do, you usually get put out to pasture in a kind of pastel retirement home. Bea, eager for something to do (and believe in), sets herself to the task of helping Calvin save the IFs by giving them someone to believe in them.

That's the loose framework upon which Krasinski's paper-thin script rests, one that gestures broadly at a kind of mechanical world-building but soon throws its hands up in the air and greedily chases one heartstring after another. Its early stretches see Krasinski using the suspenseful eye he developed during A Quiet Place to fascinating kid-horror effect. But then we get to the IFs and their dilemma, where most of IF loses its steam. The creatures themselves are hardly much to write home about: they take whatever form their kids conceived, from fire-breathing dragons to walking, talking, self-roasting marshmallows.

Sure, they're technically impressive to look at, but they're bereft of character or whimsy. That's especially true for the film's central IF, Blue (Steve Carell), a purple, snaggle-toothed furball resembling the Grimace as subjected to years of British dentistry. Rather than play him with any kind of arched eyebrow, Carell gives a surprisingly workman-like performance, a right shame given the verbal dexterity that lets him own wild animated characters like Gru.

The human cast fares little better, especially Reynolds, who coasts through this thing with the half-hearted zeal of someone sick of repeating the same Deadpool schtick. Calvin exists primarily as a smarmy sidekick, a fellow cynic who nonetheless helps the IFs on their mission. Then there's Fleming herself, a waifish young girl who rises to the occasion in a few big moments near the end but who largely gets little to do besides pout and absorb information.

The mechanics of the IFs also change on a dime depending on which lazy heartstring Krasinski wants to pull next. The script can't seem to decide how they really work: Do they disappear once forgotten about, or are they put in a home? Is the plan to rehome them to new kids, or get their now-grown adult companions to believe in them again? What's the plan from there? All immaterial questions for the presumed kiddie audience, but it's easy to get lost in the shoddy mechanics of the thing when the product as is is this listless and humourless.

IF is a well-intentioned misfire – a kid's movie without laughs and a parent's movie without purpose. Surely, Krasinski must have had a ball making it; it seems like a welcome balm after the stressors of doing two horror pictures. But now, it's time to put away childish things.