It isn’t uncommon for Hollywood to pat itself on the back for its artistic achievements, but in the case of Saving Mr. Banks, Disney must be double-jointed. Retelling – in more ways than one – the story of Walt Disney’s tumultuous relationship with P.L. Travers, author of Mary Poppins, John Lee Hancock’s film tries to psychoanalyze the writer’s reticence to let someone turn her iconic nanny into a movie heroine while celebrating the studio’s hard-won, now-legendary cinematic achievement.

Too obsessed with decoding the origins of Travers’ obstinacy to offer a balanced portrait of the author’s concerns about selling off her beloved character, Saving Mr. Banks avoids becoming hagiography of the most troublesome kind only by boasting one performance just convincing enough to overcome its self-serving “truthiness.”

Oscar winner Emma Thompson plays Travers, a buttoned-up British author who reluctantly agrees to meet Walt Disney (Tom Hanks) so he can make a case for adapting her bestselling novel Mary Poppins. Brusque and intractable, Travers agrees to sell the rights only after she goes over the script with a fine-toothed comb, discarding anything that doesn’t align with what’s in her head, or worse, cheapens the character with cartoonish pandering. But as she delves deeper into the script, Travers soon finds herself recalling the experiences that initially drove her to write the book.

After watching her gregarious father Travers Goff (Colin Farrell) succumb to alcoholism , Travers struggled to come to terms with mortality, and the unkeepable promises of adulthood. But even as she begins to yield to Disney’s ideas, she locks into a battle of wills that won’t merely determine the fate of the movie, but unveil the true meaning of the book – both on the page and in her life.

Although Hancock does his best to maintain the pretense of a balanced portrayal of both Disney and Travers – Disney cops to his commercial ambitions with the property – he inevitably stacks the deck against Travers as an inflexible shrew whose buttoned-up demeanor feels positively villainous. Of course, he also pairs that with this missing-link mystery from her childhood that explains why she’s such a jerk to the well-meaning songwriters attempting to add music to the movie, but the convenience, however accurate, of this formative experience undermines the depth and complexity of the real Travers, who was bisexual, and adopted a child when she was in her 40s – 20 or so years before the events in the film.

With the film to fall back on as evidence of Disney’s shrewd creativity, Travers can’t help but be the bad guy, disliking the songs and forbidding the use of animation – you know, all of the stuff that people like about it. But Thompson’s superlative performance almost convinces us of Travers’ nuanced transformation, allowing herself to indulge Disney’s childlike world just enough that she experiences an emotional epiphany without ever truly changing herself. (That said, the film acts as if the process of adapting Mary Poppins freed Travers’ creative juices, but she’d already written four book by the time Disney came along.)

Indeed, Thompson’s performance in the final act is a thing of great power and beauty – a case study in connecting with an audience. Although it’s widely known that Travers hated the final film – forbidding future installments and banning participation from the filmmakers when it went to Broadway – Thompson’s performance of the author’s real-life breakdown during the screening is utterly devastating, although it speaks more to the dimensions of the fictional narrative than any particular clarification of her true feelings.

As undeniably effective as those final moments are, there’s simply no getting around how self-congratulatory the film ends up being, because it positions Travers as a jerk getting in the way of Disney sharing one of its greatest efforts with the world. And moreover, reducing Travers’ objections to symptoms of lifelong trauma – only exorcised with the completion of the film – is an insult to her legacy, even if you consider Mary Poppins a bona fide masterpiece. Ultimately, it’s disingenuous for Disney then or now to position itself as the underdog, which is why Saving Mr. Banks is a resonant but hugely problematic film – a prestigious look at the embattled history of the production written by those who prevailed, while incredulously suggesting that everybody involved won.

Saving Mr. Banks opens today nationwide.