Opinion: twisting slides, a hotel room shaped like a boat and a pop-up theatre are among the "fun" recent additions to London's Brutalist Southbank Centre. Has Owen Hatherley lost his sense of humour or is there something more sinister in all these layers of entertainment?

If you approach London's Southbank Centre from Waterloo station, you will see a building which has been overrun and eaten up by Fun. Fun has nibbled away at each corner, it has struck out across its walkways and humped the concrete panels, to the point where the building appears to be wearing a permanent party hat.

Except these accoutrements are never permanent, that's part of the Fun. Some are seemingly semi-permanent, such as the skateboard park in an undercroft, recently reprieved from an ill-conceived renovation scheme, or more recently A Room for London, a minature fun boat for rent balancing on one corner, courtesy of David Kohn, Fiona Banner and Alain de Botton.

Others, such as the ubiquitous murals and graffiti, or the splayed steps that lead from the walkways to a mock-impromptu "street food market", are more transient. One or two of these would be enjoyable enough. All together they make up an oppressive kerfuffle of grinning japery.

The latest piece of Fun to be attached to the Southbank Centre forms the major part of an exhibition, Carsten Holler's Decision. Two of the artist's "signature" wiggly slides have been attached to the concrete box surmounting the Hayward Gallery. This double slide is the epitome of Fun. After a while, all this Fun becomes increasingly annoying, like someone that won't stop telling increasingly cheesy jokes.

The irony in the Southbank Centre's Fun makeover is that this "instant city" stuff was all anticipated by the building's designers. The complex, consisting of the Queen Elizabeth Hall, the Purcell Room and the Hayward Gallery, with walkways and connections to the earlier Waterloo Bridge, Royal Festival Hall and National Film Theatre, and the later National Theatre, was designed by Norman Engelback in the early 1960s for the London County Council, as a municipal cultural centre for the capital. However, it is better known for the involvement in the team of three future members of Archigram – Ron Herron, Warren Chalk and Dennis Crompton.

There's little of their later pop-futurism in this faintly sinister essay in paranoid high Brutalism, although by the time the building was finished in the mid-1960s its co-designers would be found imagining the transformation of the seaside town of Bournemouth into a centre of Fun via balloons and instant, disposable pieces of art and infrastructure not unlike those rammed into various corners of the Southbank Centre. In a sense the ideas of Archigram – the Fun Futurists – have eaten those of the same architects in their day job as LCC Brutalists.

This kind of Fun did not begin with Archigram, but with Cedric Price and Joan Littlewood's unbuilt Fun Palace, rapidly joining Tatlin's Tower as the most famous unbuilt work of the 20th century. There was much to admire in this project, the aim being to create a participatory, high-tech cultural centre for the use of the people of east London, but it has rapidly become a cliche, an image of vast cultural sheds as architectural spectacle.

The projects that have been built referencing the Fun Palace ideal have been alternately brilliant (Richard Rogers and Renzo Piano's Centre Pompidou in Paris) and farcical (Will Alsop's The Public, a short-lived Fun Palace of indeterminate function in West Bromwich).

The original Fun Palace was conceived in a context where Brutalist cultural centres were, in Price's phrase, "the Middle Ages with electricity", with no conception of what might be novel about culture in a social democracy. Given that one of the first performances it hosted was by Pink Floyd (Syd Barrett era, naturally), the Southbank Centre was not so far from this.

Its architecture, though, was determinedly not Fun, but fragmented and grey: Stanley Kubrick, not Frederico Fellini. Postmodernism was also Fun – and the Southbank Centre narrowly avoided several mooted Postmodernist makeovers in the 1980s – but Fun has come into its own in London over the last decade.

As architecture has become more sober in the British capital (the "new vernacular" of Maccreanor Lavington et al), so Fun has been concentrated in infrastructure, of a sort. The ArcelorMittal Orbit, the Emirates Air Line cable car (or "dangle way", as it's known locally), various pop-ups, and the entire career of Thomas Heatherwick, from his claustrophobic, shonky retro-Routemasters to the privately patrolled Garden Bridge he intends to foist onto a site near the Southbank Centre.

All of these present a strange, usually child-free form of infantilism, where the ideal Saturday day out could involve, if you've the moolah, a walk along the Thames taking in a frolic along the oak-tree lined bridge, an impromptu performance at a pop-up theatre outside the National Theatre, some tasty "street food" past the mural-decorated undercroft, a few trips up and down Carsten Holler's slides, a bit of austerity nostalgia shopping at the extensive range in the Festival Hall shop (a Festival of Britain-themed cushion, an Abram Games tea towel, a Trellick Tower mug?) and a night in A Room for London.

The link is firm between design, nostalgia, cutesy childishness and, increasingly, privatisation as the Festival Hall starts "moving on" political meetings and undesirables. This is all a long way from the original Fun Palace; from working class participation to a weird form of kidult tourism, encapsulated in the alternately bumptious and negligent reign of Boris Johnson, where London becomes more expensive, authoritarian and stifling as its spaces become ever more smugly ingratiating. In that context, the stern, enigmatic style of the unadorned Southbank Centre seems all the more admirable – the hope that "nothing is too forbidding for ordinary people".

The real problem with all this Fun is that it isn't really very funny – it is so overbearing that it constantly, shrilly demands you enjoy yourself. I'll tell you what's funny. At another Carsten Holler exhibition, in the Museum of Contemporary Art in Zagreb, I saw a well-dressed person in their thirties descend Double Slide, another of the artist's twisty, tubular flumes, only to get stuck half-way through.

The joy on their face suddenly curdling into irritation, fear and embarassment as they realised they were a grown adult, stuck, visible to dozens of people, midway down a slide. I don't think I've ever laughed so much in an art museum in my life.

Owen Hatherley is a critic and author, focusing on architecture, politics and culture. His books include Militant Modernism (2009), A Guide to the New Ruins of Great Britain (2010), and A New Kind of Bleak: Journeys Through urban Britain (2012).