Ahhh. That's it. I only use it on Android. Maybe I should use that feature on the PC, and thumbs down everything for a few weeks!
You can actually like/dislike stuff from the app. Expand the playback notification and you'll find the buttons there. Of course this only works for currently playing songs.
No idea why they hid it there, and there only.
Spotify app is so terrible, once you like something, it doesn't give you an option to unlike it.
Like Tinder, I really don't understand how these services -- where the magic isn't in the app so much as in the service -- who have big piles of money don't have much much better apps. It really feels like something you should be able to throw money at.
I think Apple users get the bulk of attention with regards to that. I noticed the Apple version of the same companies' apps are tighter and less bug-free. I'm on Android.