Most cheerful movies don’t open with their protagonist in a coma, narrating the events from their hospital bed. But in a fortunate reversal, director Matt Smukler’s “Wildflower” mostly grows from there, into a sweet yet straightforward coming of age drama.

“Wildflower” stars Kiernan Shipka (“Swimming With Sharks”) as Bambi, who prefers to be called “Bea” because her parents named her after a cartoon character. Those parents, Sharon (Samantha Hyde) and Derek (Dash Mihok, “Deep Water”), are both intellectually disabled, but living independently in their own house, keeping their family afloat through positive attitudes, good-natured religion and working class stick-to-itiveness.

As we learn from Bea’s flashbacks — in scenes she couldn’t possibly have witnessed or heard about from her parents — Sharon and Derek’s romance was easy for them, but difficult for their own families. Jean Smart and Brad Garrett play Sharon’s mother and father, and Jacki Weaver plays Derek’s mother, and while they want their children to be happy they also debate behind their back whether to convince them to get a divorce, or worse, medically prevent them from having children. It’s a monstrous consideration, but some of them are very, very deeply flawed human beings, and fortunately for everyone they talk themselves out of it.

Sharon and Derek have a child, they move out, and spend years living out of a van in a trailer park before they can buy their own home. From there, it’s pretty easy living for Bea, until the day her new dog runs away because Sharon left the door open — and she realizes that she’s the one taking care of them, not so much the other way around.

As we traverse Bea’s difficult teen years, working after school, getting great grades and snarking at the mean kids who make fun of her, we realize that the weight of her responsibilities has made Bea seem older than her years. But she still has a lot of mistakes to make, a lot of life to live and she may wind up abandoning her own future because her present living situation feels like a permanent moral obligation.

It’s frustrating that “Wildflower” comes out so soon after the runaway critical success of “CODA,” which has certain similarities. The greatest power in Smukler’s arsenal, after his mostly phenomenal cast, is his film’s mundanity. “Wildflower” argues that Derek and Sharon are no worse parents than any others. Sharon’s sister Joy, played by Alexandra Daddario (“The White Lotus”), has kids of her own and although she’s well off, she’s clearly overprotective to a fault. The film advocates for normalcy. It thrives in normalcy. The normalcy is the point.

Then again, normalcy isn’t always a recipe for memorable filmmaking. Screenwriter Jana Savage (“The Trap”), working from a story by Savage and Smukler, struggles the most with its convoluted framing device. Bea is in a coma, narrating her own story, even the parts she doesn’t know, but that’s not enough for “Wildflower.” There’s also a social worker played by Erika Alexander (also from “Swimming With Sharks”) who interviews every member of Bea’s family, to gain a greater knowledge of Bea’s living situation, and perhaps uncover what terrible ordeal led to Bea’s coma in the first place.

It’s a mystery subplot that seems important but ultimately comes across more like an excuse to make an uncomplicated, largely familiar coming-of-age story seem novel. But Mukler isn’t interested in darkness, even though there sure are a lot of creeps in Bea’s periphery. He focuses on warmth and acceptance, not suspicion and suspense.

Savage also has a knack for clever dialogue, even when the teen characters have a tendency to sound a bit wise beyond their years. Bea has been playing the role of a responsible adult with all the answers for a long time, it’s no wonder she’s got confidence in her views, even when they’re naive. It’s a bit of a relief to see her boyfriend, played by Charlie Plummer (“Moonfall”), point out her wisdom is practically indistinguishable from defeatism. And as preternaturally on point as that speech seems, it’s also appropriate coming from a character who successfully survived cancer at an early age, and also has a richly earned perspective of his own.

“Wildflower” can’t seem to decide if it’s a big mess or a formulaic teen drama, but when it gives us tender moments between its characters, it’s hard to really care. Kudos to whoever noticed, seemingly at the last minute, that Jean Smart and Jacki Weaver hadn’t had a scene all to themselves yet, and gave them a spot-on, funny and emotional tête-à-tête in a public bathroom. It’s just the punctuation the film needed. Smart and Weaver are fantastic, Shipka is a superstar and everyone else in this film is at least trying to make it wonderful. That they come close is, probably, close enough.