“The Comedian” is a movie about a washed up artist — played by Robert De Niro — desperately trying (and failing) to find footing in the public eye by doing something respectable with his career.

In other words, the story that “The Comedian” tells is the same as the story behind its production. Unfortunately for De Niro, the film is a comeback tale that cannot itself be a comeback due to an insubstantial screenplay. A cast full of legends does not redeem the “The Comedian”, but it definitely saves it from mediocrity.

And when I say ‘full of legends’, I mean they’re spilling from the seams like shooting stars during the apocalypse. In addition to De Niro’s iconic visage invading every scene with lovable gruffness, there are talented performers from throughout entertainment history constantly popping up in bit parts. As central comedian Jackie Burke oscillates between opportunities and challenges, the I Spy of famous faces proves more alluring than the narrative — Danny DeVito! Patti LuPone! Hey, it’s Harvey Keitel! What was happening again?

Still, Robert De Niro actually steals the show amidst all these actors that didn’t sabotage their careers. De Niro has been saddled with thankless roles for the last decade or so — especially in terribly juvenile comedies — so it’s nice to see him back in fine form. His careful delivery reminds us that he can handle gravitas and offensive humor with equal expertise.

Director Taylor Hackford (“Ray”) arranges the underdog celebrity story into something that looks like a classic indie: simple, snappy shot patterns typify modern independent film; a jazzy score recalls the low-budget Cassavetes era of old. But “The Comedian” is a mainstream wolf in indie clothing. Its weak screenplay is as familiar as any other dramedy.

It starts out exploring themes of irrelevancy and the hurdles of aging stardom, but only touches upon them lightly before drudging on to the next set piece. As the movie goes on, it devolves into a disjointed series of stand-up comedy routines and dramatic fallouts to past mistakes. It repeats this formula ad nauseam in the cloying hope to claw one more laugh or gasp from the audience, and eventually forgets to provide real closure in its ending.

This is a predictable and boring wheel of a plot. There’s an animated Netflix show exploring the exact same themes far better, and it stars a talking horse.

“The Comedian” isn’t bad, but this kind of writing isn’t convincing either. Watching talented actors uplift an uninspired script isn’t engaging. Thankfully the majority of the stand-up routines (which were written separately by comedian Jeff Ross) are pretty funny. When the other parts of the film aim for comedy, they land among try-hard jokes and outdated references.

Leslie Mann transcends the messier segments with her effervescent brightness. She manages to spark chemistry with Robert De Niro, a feat I had previously thought impossible for a comparatively young actress. For a film that boasts so many stars, their dynamic shines as one of its strongest points.

★★★ (3 out of 5)