Naples- a fantastic place, sure there are grim elements, but that's a feature of every city. If you go to Sorrento from Naples Airport/station, all you'll see is the worst. A bit like judging the whole of Glasgow because you've seen the Gorbals slums in the 60s/70s ( not an irrelevant comparison-Naples is slowly dragging itself, in a 'Glasgow's Miles Better'-sort of way, upwards).
We spent over a week in Naples this year, and never felt the need to leave it, not even for Capri.