The simplicity and density of that UI is nostalgic. You say it's crappy and incomplete, but all I'd want is a search bar which can actually scroll the whole-library view to the found-song (something I wish Spotify did, but they only filter.)

Okay fine, playlists are a good thing to have as well. Either way, I miss stuff this simple.

Implement them like the iPod used to implement playlists. There's no playlist bars, tabs, UI, or other clutter. You just had a default list you were working on, and anything you added got added to it.

Except for the constant glitching and crashing, the iPod had a really great user interface. (and to be fair, that was probably partially my fault for downloading all kinds of sketchy MP3s)