they're only a 'slippery slope to debt' if you let them! They're not some pernicious influence!
If you're in a situation (either through personality or personal circumstances) where you're likely to get into debt you can do so with or without a credit card. If you're sensible/frugal with money and in stable circumstances you'll be okay with or without a credit card.
It's the person not the plastic that incurs debt.
if you're financially solvent they can actually make you money by "stoozing."
i.e. you spend, say £10,000 on something. If you already have that £10k available, you could buy the item straight off and it would cost you £10k, no more, no less.
If you put that £10k in a high interest savings account paying 5%, and bought the item on a long term 0% card then at the end of two years you'd pay off the £10k but you'd have earned £1025 in interest (assuming you reinvested the 1st year's interest), so you'd actually only spend £8975.
And that's before you even take into account points, cashback and other incentives.
Obviously everyone makes their own decisions and risk assessment based on their personal circumstances, but if the only reason you're essentially throwing away free money is because you're scared you can't trust yourself, that's a bit silly.