The new musical drama Rocketman opens on Elton John majestically strolling into a rehab meeting, resplendent in a flamboyant Satan getup we will soon come to understand as aggressively, relentlessly symbolic. A haggard-looking John plops in his chair and rattles off his laundry list of flaws: he’s a profligate boozer and overly fond of both cannabis and cocaine, he’ll shag anything with a pulse and a Y chromosome, he has wrestled with a touch of bulimia, some anger management issues here and there, etc. The film frontloads this scene as a purposeful statement of intent, that this will be the warts-and-all biopic from which Hollywood studios tend to shy away. Take him or leave him, here’s the real Elton John, or so director Dexter Fletcher would have us believe.

The movie that follows this bold overture has no intention of following through on this declaration of imperfection, at least not with any sincerity. The script pays lip service to these vices and failings, allowing a stylish quick cut of the occasional railed line without even approaching the cyclone of dysfunction and despondency the public already knows John spiraled into being. His tantrums, mild as they are, usually stem from some provocation placing them not so far past reasonable. It’s possible that Fletcher’s simply a weak film artist, and God knows his previous work completing Bohemian Rhapsody supports the theory. But that earlier Freddie Mercury portrait also suggests a sort of corollary – that bringing a subject on to develop their own biopic can result only in dilution and creative compromise.

It’s a regrettably common occurrence, for a noted figure to shepherd their own movie treatment through production. This generally streamlines and accelerates the tedious process of development, with a marquee name attracting financiers and quelling potential squabbles over life rights. In the instance of something like Rocketman, the real Elton’s cooperation was practically a must, as the film dies without access to his deep catalogue of pop-rock hits. But allowing a person some measure of authority over their own depiction on film sets a director on a slippery slope that ends with pleasing the talent instead of challenging the audience.

At the time of Bohemian Rhapsody’s release, detractors attributed many of the Queen chronicle’s shortcomings – from twitchy editing schemes to the mismatched characterization of Freddie as a self-destructive timebomb in contrast with the decent and responsible other members of the band – to the participation of “consultants” Brian May and Roger Taylor. The vast majority of faces from pop cultural history have treated a movie as a chance to shape and secure their legacy, the exact antithesis of the form, which exists to pick apart the public’s conception of a well-known figure and then defy it.

Felicity Jones in On the Basis of Sex. Photograph: Lifestyle pictures/Alamy Stock Photo/Alamy Stock Photo

Even in the examples concerning less-famous personalities, their coming on board proves bane as much as boon. Movies such as the recent Fighting With My Family (the life and times of stereotype-flouting English wrestler Paige) or Walk Ride Rodeo (the true account of paraplegic rodeo racer Amberley Snyder’s journey back to the saddle) could not exist without the thumbs-up from the genuine article to use their likeness and story. This also has a way of defanging movies, however, with the main character’s only stroke of complexity relegated to something simple and inoffensive. In both aforementioned films, the main character shows a bit of spiky personality before taming those impulses to grow into the disciplined, inspirational force their real-life counterpart would love to be.

Sanitize these elements as Hollywood may, it’s the nasty, unflattering things that make us human

This phenomenon may have hit its nadir with the recent On the Basis of Sex, a Ruth Bader Ginsburg picture with the actual Notorious RBG’s seal of approval. Ginsburg herself had a hand in the film – we know this because it ends with actor Felicity Jones scaling the steps of the supreme court like Rocky Balboa until she transforms into the justice we all recognize – and seldom has there been a more naked act of self-hagiography. The script takes no interest in showing us any side of this woman other than the public-facing one. She’s intelligent, she’s driven, she’s not taking any guff from her male colleagues and she’s out to change America – right in line with the history books. The most revealing bits concern the rather healthy sex life between Ginsburg and her unflaggingly, almost comically supportive husband, Martin (Armie Hammer). Even then, she’s still being cast in a generous light. Ginsburg’s only sin? Fighting for the rights of her fellow women too damn hard.

Of course this inclusionary method makes for thin, flaccid, facile entertainment, but more meretriciously, it undermines the purpose of biographical cinema. Consider The Social Network, adapted from a nonfiction book that already waded through thickets of legal red tape to write about the Facebook creator Mark Zuckerberg against his will. The film faced many of the same squabbles about accuracy and fairness and a lack of generosity towards the big names that made this story worth telling. While that film’s screenwriter, Aaron Sorkin, took some liberties with the facts and drew flak for it, he also gave us one of the decade’s finest exemplars of the biopic. The film ends a lot closer to Citizen Kane than the feelgood picture book suggested by On the Basis of Sex, with our insights into an icon muddled rather than affirmed. Efforts conceived under this philosophy make the utterly true assertion that close dissection of anyone would expose real contradiction, ugliness and frailty. Sanitize these elements as Hollywood may, it’s the nasty, unflattering things that make us human. Famous types may commission the building of a trophy in their image if they so please. They should just know that that’s exactly how it makes them look: gold, plastic, lifeless.