I had a new kitchen just over a year ago and I was in a similar state to you i.e. far too many of everything really. I think it comes from having had a family, now all grown-up, then just the two of us. I've sorted things so there's one of each size of dish immediately to hand, then 'spares' i.e. those I couldn't bring myself to get rid of, put to the back of the cupboard. I know... I know ... that's not sorting, that's just re-arranging, but .... you never know.
I was horrified when I sorted the food cupboard though and had to throw a lot of stuff away - a great waste, but when something is dated 1990 something, there's not a lot of choice. This was mostly baking stuff - that essential ingredient that I only used once sort of thing. Also, why do plastic container lids breed?
Sorry, not much help, I know, but it'll be lovely when you're all done. I still keep opening cupboards just to have a quick look!