Rekordbox Slow music library. Any version. Music.app (iTunes) is also slow

I really hope someone can help me because i've been having this problem for a long time. Using audio files inside Rekordbox is very slow. Newer files seem to be faster. Older files, that are played a lot, and are in multiple playlists are very slow, for example to tag. Always rainbow wheels. Super annoying. I use Pro Dj link when DJ-ing. This is fast most of the time but also gives me issues. Every night i have 5-15 occasions where files load very slow. When this happens, it happens on al decks. Might this be due to my dinosaur music library? Due to many intelligent playlists? The reason i think my library is the issue is because i use music.app (iTunes) and have been for many years. Music.app is also very slow. My laptop is a very new macbook pro. I know for a fact that a newer macbook will not change a single thing. I really need to solve this. I still use music.app for it's intelligent playlist capabillities. It helps me compare 2 rekordbox link history playlists and generate a playlist of not played tracks, per venue. But if moving away from itunes is the way to go, i think i'll just have to. 

kind regards.