Personally I think that playlists should be viewed as virtual crates. If you’ve got more than 40-50 tunes in a playlist you might as well just be searching your collection. I’ve got a ton of playlists in my Rekordbox on various themes.
Some of the best ones are where I’ve surfed the Collection with it sorted on BPM range or Key and picked out tunes that work and chucked them in a new playlist. It’s the digital version of pulling records from your shelves and sticking them in a pile.
Agree that having access to too many tunes (digitally) is a massive headache if you are playing out. You also lose grip on quality if you’ve got 10,000 tunes at your fingertips.