Opinion: by excluding architects and focusing on research for this year's Venice Architecture Biennale, Rem Koolhaas has given the world an insight into what he thinks about architecture. The result is less than encouraging, says Kieran Long.

Every Venice biennale breeds rumours, stories and speculations. The year Aaron Betsky fell in a canal. The cat that destroyed Junya Ishigami's installation in 2010. The year the French pavilion was taken over at midnight by pot-smoking hippies. True or not, they are the tourettic tics of the fevered hive mind of architecture as it steams in the humid heat of the lagoon.

This year there were fewer stories. I saw one nearly take shape: Rem Koolhaas was leading a tour of his Elements exhibition in the Central Pavilion and getting very upset that members of the public kept joining in what was supposed to be an exclusive press event. Eventually he exploded angrily at a very nice, female journalist (who was clearly supposed to be on the tour), ordering her to stop trying to join the (very male) party that was following him around.

Not much of a story, just a sleep-deprived old man with a tender ego being rude to the nearest face he thought didn't look that important. This behaviour won't be a surprise to those who follow the architectural superstar circus. It didn't much surprise me. But the sight of Koolhaas with his ego so shredded was not a moment for schadenfreude. Elements just makes you feel unutterably sad for him and for what he thinks architecture is. That a director of the biennale, whose work and writing make him unarguably the leading architect of his generation, should make a show that proposes that architecture is, when stripped right back to 'fundamentals', the mere shuffling around of cladding, walls, doors, stairs, roofs and toilets. I may sound ingenuous, credulous. But how else are we supposed to feel?

What do you think Koolhaas himself thinks when he looks at his collection of historical toilets, in one of the back rooms of the Central Pavilion? I imagine him somewhere deep inside repeating to himself: "It has come to this." Or maybe he's laughing at us. I hope so. But both outcomes are equally lonely and both are dead ends for those of us who care about the city.

I know from experience (I worked with David Chipperfield on the 2012 biennale) that Venice directors during the vernissage are on show in a very personal way to an audience of peers from whom (despite their protestations) they need approval. For them, it is like that dream where you're naked in front of the whole school. That is psychologically demanding, and on a human level I sympathise.

But this biennale, despite its mission to provide a shared fundament for architecture, is in fact a map of the Koolhaasian psyche. It is a pessimistic, in places funny, but mostly cynical manifesto of a man so deeply implicated in the phenomena he records, that it is no longer possible to tell the difference between what he advocates and what he criticises. Each room is a like obsessive series of retweets: it is not at all clear if these quotations from others equal endorsements. I suppose this creeping ambiguity began about the time we heard him describe the CCTV project for China's state-controlled media as a "positive and shining symbol of a changing world order". These are the words from his bizarre disclaimer on his own website about the book Content. Most of us didn't know where to look, and we still don't.

You will probably know by now that the Elements show is a series of rooms curated by Koolhaas (although he put a big caveat on any authorship of the Alejandro Zaera-Polo-curated room about cladding, which he declined to talk about at all) each dedicated to a different architectural element. I won't go in to the problems with his selection of elements because Reinhold Martin does a great job of that over at Design Observer. The exhibition itself has a higher than usual number of authentic artefacts: there is a collection of real historical windows from the Brooking Collection in the UK; there's the aforementioned toilets. There are models of Chinese historic buildings from Dutch museums and walls built out of real materials. The thinginess of it all is what made some people joke that the exhibition is like a building product catalogue, but it is impressive: an encounter with the debased matter of buildings today.

Koolhaas' proposition is that architecture as articulated by most biennales doesn't really exist any more. Architects are no longer involved in most of the stuff built, and the stuff that does get put up is made of suspended ceilings and floors, of windows and cladding packages taken off the shelf. He says that the zone above the suspended ceiling is not a place of architectural activity, it has been taken over by M&E engineers and contractors. So he rubs our noses in this situation, over and over again.

Some of the rooms are nonetheless fascinating. The installation about the genesis of the Chinese roof shows how the intricate timber construction was in fact standardised in the 12th century in an empire-wide attempt to prevent corruption and overspending. It's a great yarn, brilliantly told in great detail. It is also amazing to see the bullet-shaped elevator cab that rescued the Chilean miners out of the Copiapo mine in 2010. I don't know what it had to do with architecture, but it's an incredible thing.

As you enter the room about corridors, though, you feel yourself back amongst the windmills of Rem's mind. The corridors space consists of a series non-rooms behind two intersecting drywall passageways. In it you feel like you have got out of the lift at floor seven and a half in Being John Malkovich. Suddenly backstage, it is a place where you can't tell the difference between what's a real fire escape sign and an exhibition about fire escape signs. Charlie Kaufman would indeed be proud.

This might sound amusing, but the exhibition seems to be pained by the world, depressed by looking and even nostalgic about the past. Once there was a beautiful and elegant logic to windows, infinite stylistic variation and craft skill in their making. Now we have robot arms endlessly opening and closing a window latch to test their longevity. Once staircases could articulate the subtleties of the social rank of a householder, now they are standardised by health and safety regulations.

He's right about this, of course. But he has made a biennale without asking a single architect to show their work, which means he's either unaware or wilfully ignorant of the thousands of architects engaged in precisely the topics he says the profession ignores. I can't think of a single commercial architect today on this continent who is not at least thinking about how to design out the suspended ceiling, how to use chilled beams and embed services in exposed concrete soffits and so on. It might not be an area of architectural enquiry for OMA, but it is for many, many others.

And yes, European architects build only a tiny fraction of what is built around the world every year, but Koolhaas' take is still by any standard negative. As Joseph Rykwert put it when I bumped into him under the suspended ceiling hung in the entrance to the Central Pavilion: "He tells you how it is. He doesn't tell you what to do about it."

Perhaps the key to the whole biennale comes in the only piece of authentic Koolhaas sentiment, which appears in the Arsenale as part of the Monditalia exhibition. It is printed on the floor, perhaps so it can be gradually rubbed out by passing heels, and in it the architect describes his encounter with Michelangelo's Laurentian Library in Florence. Koolhaas begins the short text by describing the "sudden urge" he felt in 2006 that led him to look for the first time at the Italian architecture of the Renaissance. He describes the experience of the library as "terrifying" and "almost like a nightmare". (This is a man who worked for many years for the Chinese government). Koolhaas does his best to describe Michelangelo's artistry in terms of the 'elements' of architecture, but even he has to admit that Michelangelo's building goes way beyond those definitions. He says in the end that the artist achieves something close to the sacred: the tourists who visit the library, writes Koolhaas, are committing "sacrilege" against Michelangelo as, ox-like, they file past.

His conclusion? "For contemporary artists and architects the lesson of the Laurentian Library is perhaps that mannerism is a dish best served cold and in small doses." Come again? Rem clearly has had some kind of epiphany at the library, but his conclusion is that this must be due to the excesses of a particular style and the solution is to limit our contact with it. This is a kind of puritanism, even self punishment. Rem comes within a whisker of the transcendent, a whole new register of possibilities for the medium to which he has dedicated his life, but at the crucial moment he draws back.

And back to what? To his rooms of 'elements', to the deep mineshafts dug into the history of building by his staff and their obsessive collaborators. After all their furious digging, Rem and his researchers find themselves in mines, with a view of a very small patch of sky, unable to see horizontally, unable to achieve the kind of synthesis that the world needs from its architects.

Beyond the central pavilion, this biennale, like all of them, is full of delights. You must go if you can, and don't miss the simply beautiful experience of Tino Sehgal's performers in the Swiss pavilion, the powerful story of the Silver Lion-winning Chilean pavilion, Sam Jacob and Wouter Vanstiphout's joyfully revisionist history of British modernism in the UK pavilion, Marco Ferrari and Elisa Pasquali's installation about the Italian alpine border or Matilde Cassani's lenticular photographs of Sikh harvest festivals in Pianura Padana. And so much more.

These are the moments where we are reminded of architecture's role as the setting for our lives, from the quotidian to the cosmic. These are the places where the citizen returns to the scene (after being banished from the Central Pavilion) and reminds us why architecture is so very important.

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Kieran Long is senior curator of contemporary architecture, design and digital at the Victoria & Albert Museum. He presents Restoration Home and the series The £100,000 House for the BBC.