A biopic of the seminal gangsta rap group N.W.A feels long overdue in 2015. It doesn’t seem especially surprising that F. Gary Gray’s take on the material has busted down the doors upon its States release, clocking up over $100 million shortly after its release. The story of Eazy-E, Ice Cube, Dr Dre and associates seems custom-made for a Hollywood interpretation – you’ve got precipitous, politically-charged success transforming into bitter recriminations and dis tracks, all mixed up with sex, drugs, violence and controversy.

Straight Outta Compton is a slickly professional take on the material, anchored by solid performances. O’Shea Jackson Jr is the clear standout playing his father, Ice Cube; the physical resemblance helps, obviously, but his committed performance demonstrates how deeply he believes in the material. Jason Mitchell is captivating, embodying the tragic arc of Eazy-E, while only Corey Hawkins – looking remarkably like Dre – disappoints. You can largely blame the writing there for failing to supply him with a three-dimensional character, but we’ll get to that.

The film is entertaining and important, but what keeps it from greatness is its lack of honesty. Nowadays, biopics are increasingly and problematically treated as works of history rather than works of art. It’s understandable – your average patron is more likely to engage with a stylish Hollywood adaptation than a dull history book – but when filmmakers set out to embrace that label, as Gray does with Straight Outta Compton, the end result is artistically compromised.

The first problem comes when you smooth over the complexities of reality to accommodate the demands of the storytellers; all historians are biased to some extent, but that’s accentuated when those historians have the title of Executive Producer (Ice Cube and Dr Dre, alongside Eazy’s widow Tomica, all possessing that title). As you’ve probably read, Dee Barnes is the chief casualty here, her beating at the hands of Dre purged from the official narrative. History is written by the winners, as they say, and here those “winners” are the guys who made the most money.

Straight Outta Compton, for much of its runtime, seems committed to erasing the inherent misogyny and homophobia of gangsta rap, rather than acknowledging that its power for social change goes hand-in-hand with such repellent rhetoric. Take the scene where Eazy-E hears his AIDS diagnosis; E’s disbelieving protest that he’s not a “faggot” is defensible in of itself. But the assurance of his doctor that it can also be transmitted through “unprotected heterosexual sex” feels like a clumsy attempt to assure its audience that their hero couldn’t have been gay. Rather than acknowledge and interrogate the less marketable aspects of N.W.A, the screenplay subtly reinforces them.

That said, E’s character is at least complex. He has flaws. He’s talented and ambitious; he’s also short-sighted, greedy and easily fooled. He feels like a real person. But neither Cube or Dre are given believable characters. They’re each moral to a fault, their only failings being too loyal or trusting too much. Flawless characters do not a good story make, and the screenplay’s repeated insistence on blaming the people around them for any less-than-exemplary behaviour is dramatically damaging, whatever your ethical viewpoint.

One of Straight Outta Compton’s bigger weaknesses is one that plagues many biopics: a lack of focus. Driven by a futile attempt to craft a ‘complete’ history of the group, many scenes are either clumsily tacked-on – think the scene where Dre meets his future wife, Nicole (Elena Goode) – or unnecessarily rushed or compressed. For example, when Dre visits Eazy-E mid-film to deliver an ultimatum – basically, drop manager Jerry Heller (Paul Giamatti) or I walk – it’s played as an honest, emotional moment, one friend reaching out to another one last time. Yet only seconds later, Dre tells E that he’s going to form Death Row Records with Suge Knight (R. Marcos Taylor), which entirely undercuts the suggested connection between the two men (if Dre was prepared to continue to work with E, would he really have made a deal with Suge already?). Perhaps this is merely a failure in framing/acting, but I’d argue it’s more symptomatic of the screenplay trying to simultaneously accommodate its emotional goals while fitting every notable N.W.A event into its runtime.

So far I suspect it’s beginning to read like I very much disliked the film, which isn’t the case at all! While it certainly fell short of expectations, Straight Outta Compton is nonetheless populated with truly powerful moments: when Ice Cube launches into “Fuck Tha Police” in a Detroit show despite express warnings from the authorities beforehand, when crips and bloods unite in the Rodney King riots and when a down-and-out Eazy-E stares up at a billboard proclaiming the intimidating success of Dr Dre’s The Chronic. But these great moments are diluted by a narrative that feels rushed despite its two-and-a-half hour runtime.

The strongest section of the film is undeniably its first act, an hour chronicling the rise of a part-time DJ, a high school student and a dope dealer to controversial chart-toppers (ignoring the small detail that they didn’t actually top the charts). That’s to be expected, I suppose; the ‘rise’ half of the rise-fall narrative tends to be the most compelling. Gray’s work behind the camera (with cinematographer Matthew Libatique) is at its best here, too. Sure, he maybe overdoes the colour correction from time-to-time, but the way the camera moves pulls you into in. It swoops, Goodfellas-style, through raucous parties. It shakes uncontrollably as a pre-fame Eazy-E flees from the police. It’s right alongside N.W.A when they’re tossed into a police van in Detroit, thudding against the wall with them. For all the calculated slickness, it feels real – as though we’re right there.

You can credit the comparative weakness of the remaining 90 minutes to any number of the problems I’ve discussed, but it’s the combination of all these factors: the smoothed-over edges of its central characters, the reluctance to tackle the darker sides of the group and the aforementioned lack of focus. The latter is particularly pronounced in the decision to give roughly equal weight to the three N.W.A stars post-split, which stretches the story to breaking point. It didn’t have to be this way! They were quite happy to forget about MC Ren and DJ Yella; why not forget about Dre?

What if this had been an Ice Cube biopic, instead? While I appreciated the film’s lack of specificity when it comes to contract disputes and the like, his character arc just dissipated as the film continued. I wanted to know more about him, about how the construction of his gangsta persona, about the backstory behind the Above the Law/Lench Mob fight, about his links to the Nation of Islam. Understand the rift between him and N.W.A beyond “No Vaseline.” Or this could have been a Dr Dre biopic, one that humanised him not through his grief over his brother, but through a more complex portrayal of his relationship with violence, both against women and his complicity in Suge Knight’s thuggery (shown in Straight Outta Compton, but largely homogenised) – a redemption story, perhaps. Or a film that more explicitly dealt with the intersection of pop culture and police brutality – a theme regularly addressed during the film, but never in any detail.

I know I’m committing the worst possible critical sin here; I’m talking about the movie that could have been, rather than evaluating the movie I saw. But then I think to movie’s best scene. Ice Cube, before a crowd of thousands, staring down his fans and the police officers among them and announcing: “Yo Dre? I got something to say.” If only Straight Outta Compton could make the same claim.