Lauren Greenfield skewered the fall from grace of two members of America’s moneyed elite in the brilliant Queen of Versailles, and returns to similar territory in Generation Wealth. This time her target is the entire edifice of consumer capitalism and concept of modern wealth, making for an ambitious essay documentary that is often brilliant but is let down by a parallel focus on Greenfield’s own family and career which becomes too sentimental and stretches the film out beyond its natural length.

The misdirection of the family and personal sequences is frustrating because otherwise, when Greenfield is talking about other people, she’s superb. Returning to the subjects of her photography from the last 25 years, she presents a cast of rogues demonstrating the psychological tragedy of wealth. We drift in and out of their lives, with Greenfield musing on wealth’s catastrophic impact personally, nationally and globally. A real highlight is former hedge fund manager Florian, an over-confident German who shouts when he gets excited and is living in exile, unable to return to the US for fear of prosecution for fraud.

We also meet Florian’s long-suffering son, and the impact of successful acquisitive parents on their children is a recurrent theme. Greenfield shot a definitive photo essay in the early 90s about rich teenagers in LA, including a 12-year-old Kim Kardashian and a young Kate Hudson. She returns to many of them – one is a dropout, one has retreated to a woodland family life (albeit still based on major wealth), and some have remained wealthy bros. All appear to have failed to show any major ambition – born into a superficial world of wealthy fame in the world’s most superficial city, keeping up consumerist appearances was the highest aim to shoot for.

If their current existence is depressing, it’s even more so for their own children, born into a world where social media and the internet more generally have made superficiality and external validation the only marker of happiness. It’s not even about actual monetary wealth any more, it’s only about show. This is miserable enough, but for Greenfield, many of these ideas coalesce around women’s bodies and western society’s manic association of sex with wealth. A former lover of Charlie Sheen and porn actress first met Greenfield when she was being fetishised for looking 14 years old despite being many years older. Desperate to escape media focus on her, she spends big money and transforms her body to be more womanly but it doesn’t turn out well because it’s still all about external beauty not inner satisfaction.

The sections on the pornification of wealth are exceptionally well constructed, and the film is enjoyably gratuitous with it, especially in grim strip and pole dancing scenes, and an uncomfortable storyline about a four-year-old beauty queen. It’s clear that the global system of wealth revolves around men dictating what women can and can’t do with their bodies, and that starts at a very early age

Greenfield’s voiceover and on-screen appearances come across as a search for meaning in all this – there’s real intelligence in a documentary that is a relentless critique of capitalism, but cleverly so, using the pop culture tools of advertising against itself – jolly music, an inappropriate light tone and the slew of sexual imagery. Her photography itself is brilliant, similarly borrowing from advertising techniques to disturb. This feels like a generational statement, a mea culpa from Greenfield’s contemporaries about making the world so awful for the next generation.

But this is why her significant focus on her own family seems so odd – although very successful, thus creating certain pressure on her children, this is a different kind of pressure and problem than the extreme inherited wealth of her other characters. Her attempt to make direct parallels between her traumatised failed subjects and her own happy family doesn’t hold water. Although a brief mention of this might have been an interesting path to explore, it’s a recurrent theme where the film repeatedly loses pace and structure, and with the entire final last chapter of the film focusing on this, the end of the film is very disappointing. The suggestion being made is perhaps that real wealth is in love and family but having just spent the majority of two hours finding little love on show in a carefully constructed argument, the film would be much better to stick to the bleakness and lose the personal stories.

• Generation Wealth is showing at the Sundance film festival