When it comes to well-known movie stars cast as famous people from real life, the record is mixed. We cut slack for Brian Keith as Teddy Roosevelt in John Milius’s magisterial The Wind and the Lion or Daniel Day-Lewis as our 16th president in Steven Spielberg’s fine Lincoln because those figures are no longer within living memory. We have very little against which to compare the actors’ portrayals.

But when stars are cast as other stars, we have millions of feet of film to judge their performances against. Because anyone in the age of streaming can see the real Marilyn Monroe, Sharon Tate, or Andy Kaufman, the task is taller for Michelle Williams in My Week with Marilyn, Margot Robbie in Once Upon a Time in Hollywood, or Jim Carrey in Man on the Moon.

Alas, the same problem is on display in the new biopic Being the Ricardos, an overlong, much-too-solemn docudrama-style portrait of the foremost couple of the Golden Age of Television, Lucille Ball and Desi Arnaz. The film was unveiled on Amazon Prime on Dec. 21 after a theatrical debut earlier in the month. Blessed with nonpareil comic instincts on camera and equally matchless business judgment behind the scenes, Ball and Arnaz, who were married from 1940 to 1960, turned I Love Lucy into a sitcom with few equals during its run on CBS from 1951 to 1957. Starring Ball and Arnaz as modestly fictionalized marrieds Lucy and Ricky Ricardo, the show induced weekly laughter in a majority of Eisenhower-era households and, thanks to generations of reruns, remains embedded in American pop culture to this day.

That spells trouble for writer-director Aaron Sorkin, who had the unhappy task of casting contemporary actors as Lucy and Desi (and, perhaps even more difficult, as “Lucy” and “Ricky”). He came up with Nicole Kidman and Javier Bardem, both of whom fall wide of the mark.

To start with, Kidman, now 54, is about a decade past the point when she could credibly incarnate Ball, who, in a film overstuffed with flashbacks, is meant to be in her 30s and 40s. Worse, Kidman, a rather portentous performer who’s never been anyone’s idea of the second coming of Carole Lombard, is far too severe. Her husky delivery recalls her performance as Martha Gellhorn in the HBO movie Hemingway & Gellhorn, not America’s favorite screwball heroine.

Kidman’s hectoring, unsmiling performance might make a certain amount of sense as Ball confronts accusations that she was once a communist and persistent troubles in her marriage, but it saps all the fun from Sorkin’s behind-the-scenes peek into the show’s making as well as his elaborate recreations of actual black-and-white episodes (felicitously deposited into the film by Sorkin, whose gift for structure remains intact). No modern performer could summon Ball’s goofy yet graceful gift for physical comedy, but a younger, less dour redhead — say, Isla Fisher or Emma Stone — might have had a better shot.

Meanwhile, Bardem, despite speaking at the usual rat-a-tat-tat clip of a Sorkin script, makes for a hulking, brawny Arnaz that suggests very little of the nimble, high-energy quality of the actual man. Again, one is left wondering what a younger, fresher actor — maybe Diego Luna? — could have brought to the table.

For his part, Sorkin seems to have been spoiled by his recent spate of movies on real-life people of real consequence, and coming on the heels of The Social Network, Steve Jobs, and especially the admirable The Trial of the Chicago 7, Being the Ricardos does seem like thin gruel indeed. Consequently, Sorkin treats this fairly trivial subject matter with an entirely unearned sense of gravity. Yes, I Love Lucy was a great show that was worked on by a great many talented people — co-writers Madelyn Pugh and Bob Carroll, played by Alia Shawkat (especially good and spunky) and Jake Lacy, are given major roles — but when, at one point, Ball narrows her eyes to imagine how a scene on the sitcom might play out, Sorkin films the moment as though Ball is dreaming up the Allied invasion of Normandy. Sorkin also takes a pretentious page from Warren Beatty’s Reds by including interview clips with actors playing aged versions of Pugh, Carroll, and producer Jess Oppenheimer (all now deceased). Linda Lavin, for example, plays an older version of Pugh.

Although the creator of The West Wing clearly has a grasp of how great TV comes together, the scenes showing an episode of I Love Lucy come into shape have nothing of the slapdash abandon of Richard Benjamin’s classic comedy about TV’s Golden Age, My Favorite Year. Everybody seems glum and humorless, especially Ball, who is portrayed always having the right answer for every scene and comic bit. (“I’m going to restage the dinner scene!”) Ball, whom Sorkin seems to regard as the Joan of Arc of situation comedy, is also shown to be a defier of network TV norms (as when Lucy pushes back against resistance to her appearing opposite a Cuban man on TV) and an unapologetic onetime communist. Whoever had the idea to turn a film about I Love Lucy into yet another earnest drama about midcentury communist witch hunts should have thought twice — scenes of Lucy and Desi referencing the Red Scare play like a Saturday Night Live parody of Good Night, and Good Luck.

The supporting cast falls into the same self-serious trap. As William Frawley, the actor who played Fred Mertz on the show, J.K. Simmons speaks with a bark and walks with a waddle, but that’s about it. And as Frawley’s co-star, Vivian Vance, Nina Arianda has a big scene or two about being pressured to stay plump because no one wants to see Ethel Mertz on a diet. Like the lamentable film adaptation of Richard Yates’s Revolutionary Road, Being the Ricardos makes 1950s America seem far more nightmarish than anybody at the time possibly thought it was.

This ponderously paced film runs two hours and 12 minutes, which, according to my math, is about enough time to watch something on the order of four and a half episodes of I Love Lucy. Which do you think is more fun?

Peter Tonguette is a frequent contributor to the American Conservative, National Review, and Wall Street Journal.