In 1989, when Thomas Heatherwick was eighteen years old, he picked up a Taschen book about the Catalan architect Antoni Gaudí in a student book sale. Inside it, he saw a double-page spread showing Gaudí’s Casa Milà, an apartment building in central Barcelona. ‘I was stunned,’ he writes in the introduction to Humanise. ‘I had no idea that buildings like this existed. I had no idea that such buildings could exist.’

The picture had a transformative effect on the young Heatherwick, who was already eyeing a career in design. He has since become a prolific and original maker of buildings and other architectural spectacles. His studio has chalked up some very significant successes, such as the delicately beautiful UK pavilion at the 2010 Shanghai Expo, the cauldron for the Olympic flame at the 2012 London Games and Zeitz MOCAA in Cape Town, a remarkable gallery for contemporary African art carved out of a concrete grain silo, which opened in 2017.

The early encounter with Gaudí also led to disquiet. If buildings could look as good as Casa Milà, why was it that so few of them did? Why were so many of them quite bad, actually? Trotting around the globe over the course of his career, he has been dismayed by dull glass towers and drab apartment blocks. Humanise is an ambitious manifesto in which Heatherwick sets out to put all this right.

Heatherwick’s argument isn’t that most buildings are ugly or badly made. It’s that they’re boring. Boringness is the root of all evil. Boring buildings make us stressed and miserable. They stunt lives and kill cities. They contribute to global warming by being unloved and disposable, meaning they are wastefully demolished after mere decades. They can even contribute to social breakdown and civil war. This ‘plague of boringness’ is ‘astonishingly harmful’ and leads to ‘starvation of the mind’. Too often this is because the buildings are designed only for their users, not for the people who have to look at them – the book has the dedication ‘For the passers-by’.

Humanise is a weighty volume, running to almost five hundred pages, but it is illustrated with the tendentious literalness of a book for children. There is an accompanying radio programme and much of the prose has the simplicity of a radio script. Heatherwick is anxious not to bore, so we are tugged along with constant rhetorical questions, portentous hooks and earthy forthrightness.

What makes a building boring? Heatherwick lists the following attributes: being too flat, too plain, too straight, too shiny, too anonymous and too serious. How come so many buildings are built this way all over the world? Heatherwick’s answer is simple and not very original: it’s the fault of modernism, which he calls a ‘hundred-year catastrophe’. He lays responsibility for this disaster largely at the door of one man: the architect Charles-Edouard Jeanneret-Gris, better known as Le Corbusier – or, as Heatherwick calls him, ‘the god of boring’. Defending Le Corbusier is a mug’s game, as one so often has to argue against the man himself – modernism’s most ardent apostles are often its worst advertisements. But it’s bizarre that Heatherwick goes so far to personalise his argument when Le Corbusier, whatever his faults, isn’t really the source of the generic flatness, shininess, plainness and straightness we see everywhere. Boring he wasn’t.

Heatherwick is uninterested in the currents of thought within modernism. The unadorned, rectilinear style he deplores has provoked at least two significant countermovements: brutalism, which favoured sculptural forms and rough-hewn surfaces, and postmodernism, which rediscovered ornament and caprice. These are blithely bracketed together and dismissed in a couple of breezy paragraphs as ‘different flavours of boring’. He doesn’t even seem interested in earlier critiques of modernism. For all his chatty bonhomie, he can be pretty vicious: poor old Louis Sullivan, the influential American modernist, gets damned for having said that ‘form follows function’, even though many of his buildings are richly decorated treasures of the sort Heatherwick wants to encourage.

His incuriosity and unwillingness to engage with the actual beliefs of modernist architects mean Heatherwick has to turn to somewhat supernatural thinking to explain their global success. Modernism is a ‘craze’, the arts were ‘under [its] spell’, modernist architecture is a cult and architects are zombies. For a book called Humanise, it is all rather dehumanising. Central to Heatherwick’s thesis is a critique of the way architects are trained and accredited, an area in which he has bitter personal experience. It’s a process he savages as brainwashing and indoctrination.

The final third of the book is taken up with Heatherwick’s prescriptions for building, a lot of which have to do with reforming architectural education and opening up the profession to artists, makers and other outsiders like him. He puts forward the modest proposal that more emphasis should be placed on the door area of a building, while also offering the impossible and grandiose suggestion that buildings should be made with a thousand-year lifespan in mind. He rightly praises the sensual, humane and inventive housing projects of the British architect Peter Barber. He thinks that architecture awards should be judged by the general public and has some unkind words to say about architecture critics. Considering his emphasis on the human, he is oddly enthusiastic about the unthinking complexity generated by AI, and promotes an app which will measure if your facade is suitably twiddly. And, presumably because it takes a cult to stop a cult, he is starting a ‘movement’, which the reader is exhorted to join.

It’s hard to escape the sense that Heatherwick is astute enough to know that his arguments are rather shaky. Yet he makes them anyway. He leans heavily on the murky empiricism of polls, neuroscience and evolutionary psychology. There’s a lot of ‘researchers have found’ and ‘surveys show’. This cannot compensate for the desperate subjectivity of his central recommendation: that ‘all new buildings that are visible to the public should be interesting’. The whole metric of ‘interestingness’ is as personal as can be, and highly elastic. It leads Heatherwick to make outlandish claims about all ancient cultures prizing ‘interestingness’ (a thoroughly modern concept) as ‘an unquestionable good’. Really?

Moreover, he does a lot of arguing against himself. He follows his anatomy of boring with a spread of counterexamples. He acknowledges that Le Corbusier’s buildings were often very beautiful and rhapsodises about his (curvy, sensual, sculptural, richly decorated, sui generis) chapel at Ronchamp. He knows that the International Style of architects such as Mies van der Rohe and Walter Gropius did more to promote flatness, shininess, straightness and so on than Le Corbusier, because he follows his assault on him with a couple of pages saying as much. But Le Corbusier is an easy bogeyman, a stand-in for architects in general, whom Heatherwick considers brainwashed zealots with perverse pretensions to art. Heatherwick knows that modernist architecture came about as a result of advancing building technologies as much as any wild-eyed ideas and that it was a response to disease-ridden slums, not Nash terraces. And he knows very well that architects aren’t the only people deciding the way buildings look, and that an awful lot of buildings, especially the boring ones, hardly get looked at by architects – because, after all the taunts, he rather briskly says as much. That dull tower of student flats, that city-centre budget hotel, that out-of-town warehouse: they weren’t designed by Le Corbusier-crazed artistes.

This weakness for eye-catching polemical cartwheels also leads to some unpleasant lapses in judgement. The use of a picture of the ruin of Grenfell Tower to illustrate his claim that ‘boring is a social justice emergency’ ought to have been struck out by an editor. The seventy-two people who died in that tower did not die of boredom. The flammable cladding that killed them was installed on a serviceable if boring modernist tower partly in order to improve its visual appeal ‘for the passers-by’.

The most annoying aspect of Humanise isn’t, however, that Heatherwick is often wrong; it’s the fact that he’s often right. There is something deeply amiss in the way that many of the spaces around us come into being. There are chronic flaws in the way that architects are trained and there should be more emphasis on practical skills. Buildings should be designed to last longer. But these conclusions are buried in copious packing peanuts of irrelevance, illogic, crowd-pleasing anti-elitism and apocalyptic hyperbole.