The Labour party is reeling from a devastating election defeat in which many of its traditional voters turned their backs on the party. If it is to rebound, Labour must take the time to understand what went wrong. And its analysis must go beyond the defenders of Jeremy Corbyn arguing that it was solely down to Brexit, and his detractors pinning all the blame on the leader and “Corbynism”.

It is also likely that the election result reflects a much longer and deeper trend, in which the party has lost the trust of communities it has long represented yet who have now lost faith in the political system to change their lives for the better.

Whatever the final verdict, the Labour party will have to change if it is to reconnect with the broad coalition of voters it needs to win back power. But as it does this, it must not lose sight of the one thing it got right in this election. Labour was right to grasp the scale of the economic and environmental challenge the country faces and offer ambitious solutions. Against the backdrop of the longest squeeze in living standards for generations, economic growth that has passed many communities by, entrenched poverty and a climate emergency, Labour offered a manifesto that began to rise to the challenge. It contained flaws, but it would have undoubtedly begun the process of transforming our economy. Those eager to reject Corbyn would be wrong to abandon this ground as well.

But Labour must learn from this election. Policies that all the polling indicates are individually popular with voters simply did not cut through: 64% of people support significant increase in public spending to invest in the green economy; 66% believe companies should be required to share their profits with employees; and 61% believe that austerity has damaged vital public services. The manifesto should have resonated with many voters and yet it didn’t.

In part, this was because an ambitious reform agenda was presented as a collection of giveaways that felt too good to be true. A 10-year economic agenda was shoehorned into a five-year programme for government and voters rightly questioned whether it could all be delivered. There was no attempt to prioritise or highlight key policies. And not enough groundwork was done in advance of the campaign to convince the public that this scale of change was not only desirable but deliverable.

Critically, too much of the change that Labour sought to achieve was top-down. Rather than pushing power out to communities, it sought change through an expanded national state with regional offices. The absence of a radical agenda on devolution was a striking omission in the manifesto. An ambition to democratise the economy too often boiled down to state ownership through renationalisation. For communities distrustful of promises from Westminster, Labour failed to tell the story of how it could deliver radical change by giving them more power and control.

As Labour dissects what went wrong, the factions defending and attacking Corbyn must learn these lessons and build from here. Abandoning Labour’s entire policy programme – as some of those who reject Corbyn wish to – and replacing it with an agenda that seeks incremental changes to the status quo would be a big mistake. There is clear political consensus that for too many people the economy just isn’t working, and also that the threat of the climate crisis is real and imminent.

Future elections will be fought and won on who has the answers to these seismic issues. Without a radical policy platform Labour stands no chance of winning back voters who despair of a system that is failing. But Labour’s response must be rooted in the people whose lives it seeks to change.

The next election will be fought after we have left the European Union and the promise to “get Brexit done” has inevitably but tragically failed to deliver the positive change those who voted for it want. All the issues that are bubbling underneath the Brexit vote will have punched through the surface – as will the anger and frustration of millions who will feel let down. If Labour can go into that election having done the groundwork, and with a manifesto that offers real change, it may just find a route back to power.

• Miatta Fahnbulleh is chief executive of the New Economics Foundation