For a political obsessive, party conferences are a treat. Whether it's the party bit (drinking bad wine by the sea at 3am in the company of half-cut, gloriously indiscreet politicians and hangers-on) or the conference bit (earnest discussions at 8am on the best way to reduce child poverty), there can be a real charge to these events, born of the sense that you never know what you are about to discover or understand.

What you hope to hear are policies that make sense of the world, and give you some faith in the future. And I ought, this year, to feel optimistic, because I heard both. Instead I am depressed. Because the policies that had promise don't belong to a single party. Each of the main parties, it seems to me, has half the prescription for the country right, and half badly wrong. Which leaves voters like me aghast at the consequences of the choice ahead.

The Tories' desire to cut spending and the deficit as fast as possible looks dangerously simplistic. If they plan to do as they say, slashing expenditure regardless of whether the recovery is established, they risk wrecking the economy and undermining their new, compassionate social policies. The history of their misjudgments over the last year – opposing the borrowing and stimulus that have kept the economy afloat – give one little confidence that they will make the right decisions in the future.

At one Tory fringe meeting a senior City figure, Clive Cowdrey of the Resolution Foundation, was emphatic that the Tories were making a fundamental mistake in concentrating purely on debt, rather than public investment. And at the Institute for Fiscal Studies, Robert Chote warns that although severe cuts will have to be made by any party, they must be well planned and cautiously implemented. There is a narrow path to be trodden between reviving the economy and pitching us into either an inflationary spiral or a depression. He fears that the Tories may arrive in office just after the start of the financial year and launch an ideologically driven instant reduction programme just as unemployment gathers pace.

If the Conservatives have got the economy wrong, though, no one could argue that Labour have got society right. Huge increases in public spending have not delivered a fairer or happier society. Twelve years in, and it isn't possible to have any discussion about public services that doesn't stray into discussing the inefficient and soul-destroying consequences of too many regulations and too much target-setting.

The chief executive of a big development agency told me that after three years in the job he seriously wondered if he had achieved anything practical at all. He had to look for money from 21 different funding streams, each with its own criteria for judging success, and he had to co-ordinate eight other agencies, all with their own performance indicators, which he had to meet. The waste, the duplication and the time spent on computers – as everyone tried to prove that they were doing what they should be doing – were beyond belief.

And this year there is a new concern: whether the state is now intervening destructively in family and community life. The story of the two policewomen forbidden by Ofsted from taking care of one another's children came out just before the Labour conference. It epitomised a growing fear that responsible adults were no longer free to make decisions in their own lives.

That's why the elements of Cameron's conference speech that talked about returning power and autonomy to communities and individuals have struck such a powerful chord. Cameron isn't appealing to the selfish individualism of the Thatcherite past. He's asking people to come together in a spirit of responsibility not only for themselves, but to one another, whether it's intervening to stop a crime, or form a school. He wants a cohesive society, but he's essentially arguing that concentrating too much power in state hands has sapped human dignity and pride.

The Conservatives plan to reverse that, in a way that is much more radical than is yet understood. Targets will be torn up, replaced by a new focus on results, and on what the public think of what they're getting. An organogram of every public service, along with details of its spending, will be placed online. The idea is that public scrutiny – why does this police service spend seven times more than that one on cars? – will become a powerful tool in making services responsive and accountable. Public servants won't look inwards to Whitehall, but outwards to their users.

This is a much more exciting approach than Labour's worn-out centralisation. But it's undermined by the context in which it will happen. The Tories' distrust of big government leads them to pull back from the heavy-handed state, but it makes them less likely to fund important social needs, and more likely to leave the economy dangerously adrift. Labour, on the other hand, is so wedded to state power that it can't distinguish between the right use – refloating the economy – and its overuse.

It leaves voters like me in limbo. The Lib Dems are no answer; they are riven by indecision about what they believe. I want a grown-up party, devoted to human flourishing, that understands the power of the state for both good and ill, and uses it judiciously, rather than ideologically. And while it doesn't exist, millions of us will feel dispossessed.