Rarely can a movement have been so hastily obituarised as Occupy Wall Street. The campaign that has done more than any other to thrust inequality on to the political agenda of one of the world's most unequal countries turned one only yesterday – yet already a would-be priesthood is reading its last rites.

Even as demonstrators began gathering in Manhattan last Saturday for anniversary celebrations, the esteemed financial columnist Joe Nocera proclaimed in the New York Times: "For all intents and purposes, the Occupy movement is dead, even as the Tea Party lives on." A similar note was struck in the news reports that dutifully totted up all the weekend arrests of protesters before bolting on boilerplate about "a cause now on the wane". In New York last weekend, I met a hedge-fund manager who recalled how his fellow financiers would froth themselves into a fury over the Occupiers last autumn; nowadays, he said, the subject barely came up.

True, Occupy no longer squats unignorably in the American or British political debate as it did last autumn. Nothing I saw last weekend resembled St Petersburg in 1917. The open assembly at Washington Square Park on Saturday night was jovial but sparsely attended, posing no disturbance to the black pensioners playing chess nearby, although they might have been put out by the dancing crusties and "tribal drummers" at Sunday's concert. And today's big march on Wall Street was planned more as a get-together than a serious resurgence.

But that doesn't justify one of the most interesting political phenomena in years being written off by many of the same folk who never saw it coming in the first place. Indeed, each time they do so, they display a lamentable misunderstanding of Occupy's strengths and weaknesses, an ignorance of how activism ebbs and flows and a complacency about the merits of its arguments.

The most ridiculous comparison is the one Nocera draws with the Tea Party. On the one hand, you have a bunch of rightwing nihilists bankrolled by the billionaire Koch brothers and with their own TV channel, Fox; on the other, you have a rag-tag group of students, the unemployed and a few others with their own Tumblr accounts. Given their different boxing weights, it is remarkable that Occupy has managed to get as far as it has, turning "we are the 99%" into one of the most resonant slogans in campaigning history.

Still critics carp at Occupy for "not keeping up its momentum", as if political campaigns ran as straight-forwardly as Frankfurt's U-Bahn. Let me cite two examples of how that is nonsense. The year before tents were pitched at Manhattan's Zuccotti Park, a US campaign called The Other 98% began denouncing "the elite 2% [who] have rigged the system". Why that flopped while another against the 1% took off is anyone's guess.

Ultimately, the history of political activism is the history of setbacks and unexpected advance. Max Berger, who helped co-ordinate the global protests of 15 October 2011 – which included the St Paul's Tent City in London – remembers planning sessions in New York being five-strong. Only on the day, and only through watching the Times Square ticker updating with fresh protests in foreign capitals, did 26-year-old Berger realise how far word had spread.

Finally, the dismissal of Occupy ignores what it has already achieved. The Zuccotti Park camp allowed hundreds of complete strangers to develop serious political arguments and strong ties alike. In the consumer onanism that is 21st-century Manhattan – a tiny island teeming with shoppers pleasing only themselves – that is no mean feat. Recently, Occupiers have begun serious campaigns against foreclosures of homes, for unionisation of workplaces and for reneging on unjust debts.

That's not enough, of course. I would like to see Occupy engage with making positive demands about what kind of future we should have, rather than what kind of present we don't. But to expect a one-year-old movement to unfurl a detailed replacement for neo-liberalism is to ask more of a bunch of twentysomethings than we expect from trade unions, NGOs or Ed Miliband and Barack Obama.

But what Occupy has got right is its targets. That the economic model is broken shows in the policy exhaustion of those still trying to patch it up four years after Lehman's collapse – and now retrying all the options that have failed already. Last week Ben Bernanke opted for a third round of quantitative easing, which will surely do more to lift gold prices than to bring down unemployment. And for proof that US politics are bust, one need only look at the finding by political scientist Martin Gilens that poor and middle-class Americans have almost no influence on which policies are made – even while laws favoured by 20% of the richest Americans have a 20% chance of being adopted by politicians. He says: "A democracy that ignores most of the public has a tenuous claim to legitimacy."

When a Princeton professor makes statements as alarming as that, cynics would be better off directing their ire at the system, rather than any ideological naivety of its opponents. Of course Occupy, and others, will make mistakes; that's what happens when you try something new. But as the activist Rebecca Solnit once said: "Despair is a black leather jacket that everyone looks good in. Hope is a frilly, pink dress that exposes the knees."

Happy first birthday, Occupy. Keep showing your knees.