I’ve been doing this with both my vinyl&CDs & iTunes.
iTunes was just a mess with everything duplicated and a load of shit that I’d randomly downloaded at different points. Ended up rediscovering maybe 50 albums I only have on download that I had basically forgotten about. Most aren’t on Spotify either so really worthwhile and have been great to listen to. Might put them on cassette so I have a mini distinct collection.
Also spent Christmas/New Year break sorting through vinyl and CDs. Just felt whenever I browsed I never got past the stuff I never liked. So I weeded out about 300 in total - approx 100 vinyl albums, 100 cd albums & 100 12"/E.P/7".
Most of the CDs are things I bought based on pitchfork reviews I hated. Took me a while to learn my lesson. 
Feels great already as my collection really feels like it actually reflects my tastes now. Some stuff I left is probably only for the odd nostalgia listen but I haven’t kept anything that I feel hasn’t stood the test of time. Basically if it’s in my collection now it is stuff I enjoy listening to.
Going to see if I can sell some stuff on discogs but otherwise am happy enough to clear some stuff out to charity shops.