Sir Ian McKellen is 85 years old, and one can see why the renowned British actor took on the lead role in the new movie “The Critic.” The part affords him the chance to play a range of emotions, deliver the occasional tart line of dialogue, and generally commandeer every scene he’s in — the kind of role not many over-80s are offered. Unlike, though, this summer’s hit “Thelma” with the 94-year-old June Squibb in a sparkling role, Mr. McKellen’s film leans on tragedy instead of comedy, thereby turning what could have been wickedly articulate fun into a mishmash.

The film begins breezingly enough, and viewers might think they’re in for a flip, light satire in the mode of Stephen Frears (“The Queen,” “Philomena,” “Prick Up Your Ears,” etc.). Mr. McKellen plays Jimmy Erskine, a theater critic for the Daily Chronicle in 1934 London. The paper’s owner has recently died and it is now headed up by the middle-aged heir, David Brooke (Mark Strong). Jimmy is known for his excoriating style of criticism, and David warns him to “be kinder.” 

One of those often at the receiving end of his opprobrium is actress Nina Land (Gemma Arterton). In an early scene indicative of the movie’s muddled approach, Nina confronts Jimmy about his persistent printed ridicule of her abilities and, upon discovering he has a proclivity for rough trade, threatens to expose him. Astonishingly, Jimmy responds to her blackmail by enlightening her with the idea that they’re similar, that she enjoys humiliation and danger — of the stagefright sort — just as much as he does in his private life. 

This scene is set outdoors during the daytime and, though outrageous and tonally erratic, it does provide a respite from the constant red-orange light bathing nearly all interior and nighttime settings. Had cinematographer David Higgs visited Russia’s famous Amber Room shortly before filming and decided that its darkly golden atmosphere was a mood match for anxious, depressed 1930s England? Whatever the inspiration may have been, the lighting transforms the players into waxwork figures, embalmed in reddish resin.

When Nina later comes calling at Jimmy’s apartment, he reveals how he once was an actor and gives the actress some advice: Less is more. Mr. McKellen might have taken his screenwriter’s advice. Throughout the film, the actor hams it up — but not comically so — embellishing moments with gesticulations and bits of actorly business, though his voice remains expressive and nuanced. 

My personal affinity for someone with a “critical” disposition aside, I found Jimmy a difficult character to get on board with, and I imagine most viewers will, too. Still, it’s a testament to Mr. McKellen’s courage and prowess as an actor that he doesn’t downplay Jimmy’s unpleasantness or devouring ego.

When wit shines through the viscous gleam and pseudo-seriousness, the picture flashes with real moments of intelligence and entertainment, such as when Jimmy discusses literature with a fellow critic, or during an encounter with fascist Blackshirts. Also, after he and his assistant/sometime lover, Tom, are arrested, and Jimmy is subsequently given a month’s notice by the newspaper, the movie’s comingling of history and contemporary issues does begin to congeal. Racism (Tom is Black), homosexual discrimination, antisemitism, class warfare, and more are addressed in Patrick Marber’s fitfully clever script, though their mentions feel clunky.

Once Jimmy makes an unethical proposition to Nina in order to get back at his employer, the film turns darker and wobblier, with what little fun there was to be had exiting alongside the plot’s plausibility. Thankfully, Ms. Arterton outlines Nina with such tender shading that even while her character is rushing headlong into misery, one still understands her desperation. The rest of the roles are either underwritten — Tom, in particular, despite Alfred Enoch’s geniality — or nearly nonexistent, with the great Lesley Manville wasted as Nina’s mother.

At one point, Jimmy expresses how he finds no enjoyment in theater, despite reviewing it. This cynicism seeps into how director Anand Tucker steers his movie, guiding it into both stately dreariness and a frazzled climax, where melodrama is mistaken for tragedy and on-trend themes stand in for the story’s moral. Indeed, its pessimistic, almost-woke politics might have been more acceptable if the tone had remained light and understated. 

Ultimately, “The Critic” aspires to say something acidically honest about ambition, power, and the old guard, but it’s not nearly as tough-minded as it thinks it is. One imagines that Jimmy himself wouldn’t be very kind to “The Critic”: He’d likely deem it a farce masquerading as drama.