An extended sitcom with surprisingly little comic bite, “Adult Beginners” aims to be a breakout vehicle for Nick Kroll, but its mildness does him absolutely no favors.

Written by Jeff Cox and Liz Flahive and limply directed by producer-turned-helmer Ross Katz, the film introduces Kroll as Jake, a well-heeled New York entrepreneur who loses his wealth—and the tolerance of most of his investors—in a catastrophic rollout of a piece of electronic paraphernalia called Minds I, glasses that will supposedly open the world of the Internet—and beyond—to their users. Broke and friendless, he repairs in disgrace to his childhood home in the suburbs, now occupied by his pregnant sister Justine (Rose Byrne), her husband Danny (Bobby Cannavale) and their three-year old son Teddy (Caleb and Matthew Paddock).

Danny, a friendly, gregarious sort of fellow who’s fixing up the place with an eye toward selling it, suggests that Jake could carry his weight around the place by taking care of Teddy while he and Justine, a teacher, are at work, saving them the cost of daycare; he even offers a token payment of $300 per week. Of course, initially the hyper-active kid proves too much for his uncle to handle, but it seems like no time at all before the two are bonding. Jake also strikes up a relationship with Blanca (Paula Garces), a nanny he meets while taking the boy to the park.

Everything can’t run smoothly, of course, and so the script introduces a potential speed bumps—Jake’s discovery that Danny has enjoyed a date at a massage parlor with a pretty co-worker, his receipt of a job offer at a tony financial firm—and rather tiresome secondary characters (a loose-living bachelor friend of Jake’s back in the city, an erstwhile high-school classmate) are introduced to provide a semblance of variety. But the movie is basically about what so many are—the importance of family—and the point is made in crushingly obvious form toward the close, when Jake has to choose between putting his job first or racing off to be with his sister when she needs him. There’s very little doubt about what his choice will be.

Kroll proves himself adept at delivering supposed zingers, as well as scowling and rolling his eyes on cue, but there’s a phlegmatic quality to his performance, as though he were constantly waiting for a laugh track to kick in. Far more capable are Byrne and Cannavale; she brings a bright, engaging, slightly ditzy likability to Justine, while he once again conveys perfectly the image of a laid-back, genial middle-class guy who enjoys sneaking out for a joint every once in a while. Garces is pleasant as an easygoing girl who doesn’t mind when Jake’s sister tags along on what’s supposed to be a date, and the rest of the supporting cast gets by without offering much that’s special.

In the final analysis, though, “Adult Beginners” is just too familiar, and Kroll’s shtick doesn’t raise it above the ordinary. The title, incidentally, refers to the fact that Jake and Justine join Teddy in his swimming lessons despite the fact that they have to overcome their fear of the water. The movie itself neither sinks nor swims; it just floats along on a current of bland affability that identifies it as yet another sadly toothless American independent comedy.