I love and still use WinAmp and do not use any streaming -- but what changed is how people listen, thanks to iTunes and iPods etc and then Spotify. Everything is based on playlists and artist selection leaning away from albums/releases. It changed how people load up music, introduced a huge rise in 'random' playing that was way different than previous era of CDs where you'd pick an album and play it, or listen to radio and DJs are selecting things (perhaps the 'DJ' selecting has just been replaced/attempted to be duplicated locally by software I guess). The way people listen changed. Not a fan of it at all, but that's where the 'unsolved'ness comes from. IMO the way people listen became even more passive and lazy and the huge portion of the market that just streams whatever puts little to no effort into their music (read: people who 'like all kinds of music') and that's what's just fine by Spotify.

The UI is still the same though. A big grid of Song - Artist - Album. Everything is fundamentally based on that, whether that's your entire library, a playlist, or filtered by something else.

Everything else is an addition, but somehow modern apps have managed to make the basic grid worse too at the same time.