The API, for example. It's a ton of fun to bang out toy projects.
Just the other day I built my own podcast picker script that curates a playlist of subscribed podcast episodes in exactly the way I want (balance-wise/order-wise). Sounds minor, but it has been huge for my smart-home listening experience, given how terrible the out-of-box podcast experience is with Alexa.
I've also noticed songs disappearing from my library, & crappy recommendations in Spotify. What service did you end up going with?
I tried three competitors as I moved away from Spotify, and found they were all substantially better than it.
I care about music selection, recommendation quality, and library stability (not deleting stuff from my collection).