Last time the Tories had a leadership problem, they settled on Theresa May as the solution. That isn’t a mistake the party will make again, although other mistakes are available. Half of the cabinet and just as many backbenchers are parading themselves in speeches and newspaper articles. The competition to be the Conservative party’s next problem is under way before the current problem has stood down.

The usual practice when picking a new leader is to overcompensate for faults in the old one. May’s methodical chilliness appealed as the antidote to David Cameron’s careless charm. The same trait, expressed as lack of agility and diplomacy, made her a poor choice to negotiate Brexit. But it is easy to say what May got wrong. The more interesting question is what she almost got right.

May came to No 10 imagining that her time there would not all be spent on Brexit. Her ambition was social change. She envisaged a legacy for herself as the leader who unblocked the sluices of wealth and opportunity, washing away the anger that had provoked so many to vote leave. Many of her MPs believed it too. Brexiters thought getting out of the EU would be easy, and remainers thought May’s seriousness equipped her to handle the difficulties. Both camps thought a massive majority in any general election was in the bag because Jeremy Corbyn was leading Labour.

Those assumptions were wrong. Three years have been spent failing at Brexit, failing to address the causes of Brexit, and bolstering the credibility of the opposition. May’s deficient character is only part of the explanation. There was no route to a united Conservative party in 2016 because none of the challenges confronting Britain were going to be resolved by leaving the EU. And in 2019, more Brexit is not a serious answer to any question that might be asked of a Tory leadership candidate.

One lesson Conservatives might take from recent years is that limiting the supply of government doesn’t automatically shrink demand. People still want and need the services that are cut. By contrast, the promised benefits of fiscal discipline (a more solvent future) are abstract. A party of fiscal disciplinarians only gets a political dividend if voters think the nasty medicine is necessary, which many did when Labour was sucking up blame for the financial crisis, but that effect has been degraded by time and events.

Labour is now unapologetic in promising a government that would do and pay for things. And while there are clearly reservations about Corbyn as prime minister, voters do like getting stuff. They certainly prefer it to having stuff taken away. Spooked by that observation, May last year declared an end to austerity, which was supposed to close down Labour’s attacks but ended up sounding like intellectual surrender. The chancellor found £20bn for the NHS yet it made no difference to the party’s reputation for meanness. Conservatives cannot outbid Corbyn in public benefaction. If May promised every voter a holiday in Tenerife, Labour would offer to fly them to Elevenerife.

Sajid Javid, Amber Rudd, Jeremy Hunt and Boris Johnson Composite: Reuters; Getty; PA; AFP

A counterweight in that argument would once have been the Tories’ reputation for financial sobriety. Brexit has shredded that. Since Britain’s future relationship with the EU is a mystery, the government doesn’t really have an economic policy. The whole project is driven by people with millenarian faith in the redemptive properties of chaos. That makes it hard for Tories to argue that Labour policy would be worse. Worse than what?

There is no going back. Tory members believe Brexit is a brilliant idea, and candidates in a leadership contest will have to share that belief or simulate it convincingly, which boosts the prospects of idiots and charlatans. A field led by Boris Johnson and Jeremy Hunt is not one in which plasticity of belief is a handicap.

It doesn’t help that Brexit mythology is suffused with crass libertarianism that believes the best thing government can do for people is cut their taxes, then leave them alone. That is not May’s creed, which is one reason why she made an uneasy partner for Eurosceptic hardliners. The prime minister is not averse to state-sponsored social activism, but she has lacked the political bandwidth to develop that instinct into a governing philosophy. She is also limited by a parochialism that was better suited to the Home Office – looking out at the world through narrow, suspicious lenses, fretting about security and counting foreigners.

Her successor will need to scan a wider horizon, grappling with problems that do not have discrete national solutions: climate change; the unaccountable power of technology giants; the disruptive impact of artificial intelligence; rivalry between a rising Chinese superpower and a maverick American one. How politics copes with those issues has knock-on effects at street level. People who already feel disoriented and marginalised by globalisation are going to need a lot more help adapting to what comes next.

Britain is going to need a level of interventionist government and European engagement that is deeply unfashionable among Conservatives. Some MPs understand this, and might even dare to say it aloud in a leadership contest. But the larger section of the party does not like the feeling of new realities intruding on old beliefs. Their reluctance to adapt is driving the embrace of aggressive culture wars, economic delusion, nationalism, Trumpism.

The choice is between a difficult, honest conversation about the causes of public discontent and an easy, cynical campaign to distil the anger into electoral fuel and ignite it. It is clear which path a responsible party of government would take. But who, looking at the Tories now, sees such a party?

• Rafael Behr is a Guardian columnist