Forget the parched wasteland that is Brexit Britain in bleak midwinter. Let me take you to a place where the political terrain is so radically different as to be idyllic. In this land, rows of cheap starter homes neatly line the blossoming streets of new garden cities, and no twentysomething frets about getting on to the housing ladder. Not a solitary infant goes to bed hungry. And when you or your loved ones fall ill, a trusty family doctor is on call from 8am to 8pm, all seven days of the week.

Already I hear you rumbling like a famished teen at Nando’s: where is this paradise? Sweden or, at the outside, Singapore? No, my friend: it is the UK in 2020. Or at least, it was supposed to be, because all of those treasures and so many more were promised to arrive by this year by the serious, sober all-powerfuls who run the country.

Remember Gordon Brown? Practically the first thing he did on becoming prime minister in 2007 was vow to build an extra 3m homes by 2020. Many would nestle in 10 new “eco-towns”, into which he pumped millions of taxpayer pounds. Big, bold and more sprawling than Jacob Rees-Mogg on a parliamentary bench, it was a classic Brown plan. Except at the finish line we can see that not a single eco-town ever got off the drawing board, while the UK has built only 1.9m homes. Far from being fixed, the housing crisis has grown.

Another scheme that never got beyond a slogan was Tony Blair’s cast-iron guarantee in 1999 that within two decades no child would live in poverty. Ambitious and inspiring, it was soon dropped and replaced with a more modest target. And that seven-day GP service was dreamed up by David Cameron, who guaranteed it would be UK-wide by this year. Then again, this was the same man who planned to remain prime minister until 2020.

No other year has been as loaded up with targets, goals and predictions as 2020. Over the past two decades, governments red and blue have regularly given their grandest objectives this deadline – near enough to imagine yet sufficiently far away not to act. And so the most prophecy-laden year of the century is also the one that will most brazenly shortchange us.

Time after time, some beleaguered secretary of state has delivered a speech or released a strategy that swept the thorniest problems in his or her portfolio into a “2020 vision”. It wins them headlines and buys them breathing space; and in a more serious political culture they would now be being held to account. But no – because this is Britain. So let us count our squandered inheritance.

Let’s remind ourselves how Brown once pledged that in 2020 no car showroom in the country would sell new gas guzzlers, only electrics or hybrids. Or his 2010 assurance that by now every home in the country would enjoy superfast broadband, with the UK outstripping Silicon Valley to become “the world leader in the digital economy”. Whatever you thought of Jeremy Corbyn’s free broadband offer at last month’s election, history reminds us that some ideas just keep coming around, like orphaned suitcases on an airport carousel.

As chancellor, George Osborne swore he would pull government finances back into the black by 2020 – an oath that became government policy in 2015, only to become history the year after. Hopped up on his “march of the makers”, he launched a crusade to double the value of UK exports up to £1 trillion by this year. He must have known it was pie in the sky. At £675bn, today’s export total is stuck far below his target while the UK’s trade deficit continues to balloon.

Will any of the 2020 targets be hit? Yes, that set by Blair to get 20% of electricity from renewable energy. But that was part of an EU-wide drive with Brussels checking and chivvying on progress – the same Brussels to which in three weeks’ time we bid adieu.

I could carry on in this fashion, a journalist playing skittles with Westminster’s failed resolutions and asking Dude, where’s my utopia?But that ducks the bigger question: what damage have these broken promises done to our politics? All the pledges were made long before the all-out lie-fest that was the EU referendum of 2016. None were stuck on a fibbing bus. Yet government ministers must have made many of these solemn vows with fingers crossed behind their backs. In their corner were civil servants forsworn from peddling porkies. Former mandarin Jill Rutter describes Whitehall’s justification for this reciprocal make-believe as: “We won’t tell you that it can’t be done if you won’t sack us when it’s not done.” And she is only half joking.

Perhaps it helps that every two-bit consultancy and business guru has wallowed in 2020-ism. In 1998, the Henley Centre predicted that by today “the longest commuter journey will be just under two hours, mainly for the very wealthy using the space shuttle”. Yes, it did really predict that. Countless managers have used the year as the peg for some catastrophic transformation, such as those at Manchester University who embarked upon a “2020 strategy” promising to improve staff satisfaction while driving up earnings. Instead, the university starts this decade at war with swaths of its workforce and clunking through vanity building projects even while its credit rating keeps slipping.

Tying this together is a belief in what the Henley forecasters dubbed “friction-free capitalism”. The 2020-ers thought they had capitalism sussed. Nowhere on their horizons was there a global banking crash, let alone a lost decade. Add to that a belief among Blair and his heirs that they also knew how to win at politics. This school of thought focused on retail and salesmanship – which, as University of East Anglia professor of political theory Alan Finlayson observes, were driven by big “offers” designed to grab headlines rather than worrying too hard about delivery.

Yet even while Blair and Brown, Cameron and Osborne were staring into the middle distance and describing the shimmering visions ahead, their voters saw institution after institution engulfed by crisis: high-street banks, MPs over expenses, the press with phone-hacking, local councils and public services butchered by cuts.

What value in a glorious future when the present is so chaotic? What’s the point of grand designs drawn up in Westminster when daily life for the public is a prosaic mess? In that gulf has bred the nihilism that threads through Brexit alongside contempt for politicians, now seen as so untrustworthy that one might as well stick a serial liar in No 10. Boris Johnson famously loves a legacy project – an airport island here, a garden bridge there. The difference this time is that when our blonde Nero promises voters a grand target, not even his own side will waste a second believing it.

• Aditya Chakrabortty is a Guardian columnist