I don't know if you are being sarcastic asking where the debt has come from.
In case you are serious - too many public sector workers v private sector, too many benefit claimants, services that we can't afford anymore ie the NHS, wealthy leaving the country, avoiding work being rewarded, illegal migrants being housed in hotels costing a fortune.
Another big problem with our debt is that each month we borrow more to pay for our bills. So each month our debt goes up and thus the interest on the debt goes up. As we become seen as less stable and less of a good investment rates on our debts go up making this burden even greater.
The only way out of a spiraling black hole is to stop adding to the debt and start reducing it. How do we do that. We need more income (so cut benefits and get people back to work), we reduce costs (cut benefits, throw out migrants, stop funding a NHS we can't afford). As our debt burden goes down and our income goes up we can start investing in the country with new infrastructure etc
No failing services are not a new thing which is why people are saying well the Tories couldn't fix it, the labour party couldn't fix it so hmmm maybe we should try someone different with tougher views.
Is that more scary than continuing the way we are? If I saw labour making good decisions, slowly and surely then I would accept that it would take them quite a while to fix things. However I don't think they have done this at all and so here we are......