It's my most used app by far. As far as aesthetic goes, I am totally in love with the green and black scheme that has been Spotify's trademark for years now.
But you know what could make Spotify even better? A social tab.
Yes, there is a live feed of what your friends are listening to on the desktop version. But you can't really interact with it.
If Spotify could add a new "Social" tab (along with the current Home, Search, and Your Library pages), interacting with friends would become so much easier.
The tab would include whatever your friends are listening to, but also an area where you and your friends can add a "Highlight" section. In the Highlight section, you can post any song/playlist/album/artist that you are currently listening to. Whenever a friend visits your profile, they'll be introduced to your newest hits!
This new social tab would also make it much easier to navigate to friend's pages, especially on the mobile version (which most users have).
And there are so many more ideas that can be added to a social aspect! This is just the tip of the iceberg!