How might “L’Immensita,” the new film by director Emanuele Crialese, come across 15 or so years from now — that is to say, when the controversies surrounding transgender people have achieved a cultural and sociological equanimity?

Time, after all, does have a way of tempering the bumpy straits of history. At this moment, audiences can’t help but watch “L’Immensita” — a picture that is largely about a teenager who feels she’s a boy — and be aware of just how au courant it is. For some this will count as a marker of progress and acceptance; for others, it will be seen as a bandwagon gaining alarming traction.

Some of the most striking movies in recent memory have, to one degree or another, encompassed trans characters. I’m thinking, especially, of “Dos Estaciones” and “Joyland,” the stunning debut film by Saim Sadiq. “L’Immensita” doesn’t quite come up to the snuff of those films for reasons that have less to do with its presumed relevance than with Mr. Crialese’s inability to make up his mind as to what his movie might be.

“L’Immensita” is a disjointed venture graced by flashes of truth and moments of brilliance. Mr. Crialese, who co-wrote the screenplay with Francesca Manieri and Vittorio Moroni, puts his emphasis on the trials of Adri (Luana Giuliani), a young woman who prefers to go by the name Andrew. Adri/Andrew has two younger siblings, the precocious Sara (Maria Chiara Goretti) and Gino (Patrizio Francioni), a child whose chubbiness is less of a concern to his family than his habit of regularly defecating in a closet.

These are children of a privileged Spanish family living in an upscale apartment on the outskirts of Rome. The occupation of their father Felice (Vincenzo Amato) is never clarified, but it keeps him busy enough that he’s rarely at home. When Felice does show up, the atmosphere couldn’t be more tense or tight-lipped. Clearly there’s something awry with his marriage to Clara (Penélope Cruz), but, then, there’s something awry with Clara herself.

Clara isn’t so much a mother to her children as a companion. She’s prone to outbursts of playfulness and energy that are noticeably at odds with her status as a parent and as an adult. When Adri, Sara, Gino, and a bevy of cousins get lost at a large family affair, Clara exhibits the requisite alarm. Yet when the children are discovered and subsequently admonished by their mothers, Clara breaks the tension by staging a water fight that goes on for longer than anyone is comfortable with.

The finest scenes in the film are those dedicated solely to the children. The interactions between Ms. Goretti, Mr. Francioni, and Ms. Giuliani are remarkable in their clarity and chemistry. When our heroes are plunked within a myriad of uncles, aunts, cousins, and grandparents, “L’Immensita” comes alive with an intimacy that will ring true to anyone conversant with the myriad tensions and tendernesses that accrue from family.

The problem with Mr. Crialese’s picture is the nuclear family at its core. Although the world of the children is brought vividly to life, their parents aren’t characters so much as ciphers saddled with pedantic shortcomings. The character of Felice is especially underdeveloped, being a throwback to someone’s abusive idea of The Organization Man. Mr. Amato’s talents are wasted here.

Ms. Cruz’s star power does much to compensate for Clara’s relative one-dimensionality. Can this woman never not light up a screen? Yet her character, in the end, doesn’t elicit much sympathy, being an emblem of mental illness rather than a woman bearing real troubles. And, please, let’s not mention the musical numbers wherein Mr. Crialese succumbs to postmodernist affectation in the service of self-expression. The kids in “L’Immensita” deserve better, as does the audience.