“I Used to be Famous” is a sweet little nothing of a feel-good comedy, a sometimes cloying wish-fulfillment fantasy about a pop music has-been and his new drummer, an autistic prodigy with the sticks.

It’s built around a winning turn by Ed Skrein and a little movie magic — or magical interpretation of “on the spectrum,” something screenplays bend and over-simplify because they can and because they must if they’re to have their onscreen “wish” fulfilled.

Skrein, of “Midway,” “Deadpool” (he was Ajax) and the “Maleficent” sequel, plays a 40something veteran of Stereo Dream, a Brit boy band that was all the rage in the early 2000s.

Vinnie D used to be blond and “used to be famous.” Now he’s reduced to towing his keyboards around on a cart as he hits up bars around his Peckham, South London neighborhood, begging for a gig.

His noodling at the synthesizer sounds amateurish, in that “anything that comes out of a synthesizer sounds musical” way. We’re not surprised when we learn he was “self taught.” Even in his heyday, his actual skillset was limited to his looks, his swagger and the way his average voice blended in with others.

Busking inane notes at a street market, powering his keys with a car battery, insulted by the one local who remembers who he used to be, Vincent finds himself accompanied by a teen who won’t make eye contact, and won’t take a hint that his impromptu drumming on the metal railing of a bench isn’t wanted.

But the kid finds his groove and the duet takes something like a pleasant form. That’s when Stevie (Leo Long) is finally hunted down by his worried single mom (Eleanor Matsuura of “The Walking Dead,” “Wonder Woman” and “Justice League”). He’s spirited off before Vinnie can finish thanking him.

Someone, of course, recorded that duet and it’s almost going viral, which has Vinnie pursue more gigs, and hunt for the mysterious DIY drummer — whom he stumbles into at a drum-circle/music therapy session at a local rec center. All he’s got to do is convince mother Amber to let him drag her special needs son on stage, in front of crowds, to play his drums…and pans and pots and whatever.

Director and co-writer Eddie Sternberg makes his feature directing debut an expansion of a short he filmed earlier, and I like the way he depicts the creative process and the chemistry Skrein and Long develop. Their “first gig” is encouraging and uplifting, right up to the point when a single audience member brings it all down, an all-too-common occurrence, even before our boorish era blossomed.

But the movie is so predictable as to be drab and dispiriting. Vinnie hits up his still-famous former bandmate (Eoin Macken) for help, there are “management” issues, and all the while, Amber is bristling at the situations this selfish stranger is putting her vulnerable child in.

Stevie isn’t the easiest sale for Vinnie’s “let’s get famous together” pitch.

“It’s not about being you, is it?” Vinnie believes. “It’s about being SOMEone.”

The subtexts, of meeting your potential, regrets over selfishly putting yourself first, paths not taken (Amber used to be a dancer) are just as predictable as the glib way the film treats autism and drumming as something that will transform Stevie.

Maybe. Maybe not.

The music is mostly forgettable. Skrein has a nice, flat, unschooled crooner’s voice.

Coupling those not-exactly-assets to a story without a single twist you can’t say you didn’t see coming, the best one can say about “I Used to be Famous” is that, all things considered, it’s harmless, and not entirely charmless.

Rating: TV-14, profanity

Cast: Ed Skrein, Eleanor Matsuura, Leo Long, Eoin Macken

Credits: Directed by Eddie Sternberg, scripted by Eddie Sternberg and Zak Klein. A Netflix release.

Running time: 1:44