The Comedian Robert De Niro, Leslie Mann, Danny DeVito. Directed by Taylor Hackford. Rated R. Opens Friday in select theaters.

For many years now, Robert De Niro has demonstrated a willingness to appear in pretty much any movie that can meet his quote, from straight-to-video thrillers to lowbrow comedies. At first glance, The Comedian looks like another one of those projects, a chance for De Niro to shamble through a half-hearted performance in a poorly constructed movie. But this dramedy about a formerly famous comedian looking for a comeback is actually a De Niro passion project, a movie he has been attached to since 2011, as various directors came and went. It’s hard to imagine what sparked De Niro’s excitement about the script, though, and his performance doesn’t indicate a level of engagement above his work in a movie like Dirty Grandpa.

Even more distressing, the humor in The Comedian is often at the same level as Dirty Grandpa, as De Niro’s Jackie Burke tells scatological jokes that are meant to be shocking and subversive, but sound like they were written by giggly 12-year-olds (late in the film, Jackie goes viral with a song parody called “Makin’ Poopie”). Decades ago, Jackie was the star of a broad family sitcom, and he’s been trying to match that fame ever since. After attacking a heckler, he’s sentenced to community service, where he meets fellow convict Harmony (Leslie Mann), with whom he strikes up an unlikely romance.

De Niro and Mann have no chemistry, and their relationship proceeds in fits and starts, as the overlong movie takes long detours to show Jackie’s stand-up work. De Niro never looks comfortable onstage, and Jackie’s supposedly hilarious, scathing material is painfully dated and unfunny. It’s one thing to let De Niro off the hook for appearing in a terrible movie for the paycheck; in The Comedian, he has no such excuse.