Basically, we have a whopping big loan outstanding. It goes up each year because we can't afford to pay off the capital part of the loan.
The amount by which it goes up every year has decreased under the Tories. So whilst we're screwed, we're less screwed than we could have been.
As for taxes, they are used to influence spending. Corporation tax goes down... the aim is to encourage more businesses to come to the UK. If existing companies in the UK pay less CT but lots of new companies who weren't here before and not paying CT before start paying CT, overall, quids in.
Giving an allowance for a tiny bit of employer's NI? Designed to encourage one-man bands to hire a second person for cheap and thus create another job, thus getting someone off jobseekers (whether it's that second person directly, or say, the person who takes the job that the second person leaves in favour of this new job).
Now, tax policies don't always have the impact that they're meant to. But the intention is there.
This is one of the reasons why I remain pissed off that tampons are not zero-rated and thus apparently not treated as an essential item of expenditure. I don't care if the VAT from tampons is ring-fenced for women's charities; there are some women who need tampons who could do with the tax break at source. There's using tax to manipulate public spending for the greater good and there's bloody well interfering too damn much. No VAT on sanitary products, that's what I say.