Somebody I know also had this issue at one point. In his case it was girlfriend which also used his account (but apparently without creating playlists or hearting anything, idk).
In my case I imported my Rdio history so it’s possible that something went wrong with a difference between loading albums & seeding the recommendation engine. It was really weird because I was expecting better based on most of the other users I knew.
The import could have something to do with it. When I started using Spotify I used a playlist importer that included many false positives when it couldn't find a particular song. I ended up with a bunch of live David Bowie recordings that I've never heard in there, and now it still thinks I want to hear him every time I shuffle my liked songs. It could have chosen a worse artist, but I don't need to hear him every time.
Talking about Discover Weekly playlist: I think the recommendation engine is mostly based on what you actually listen to. When I listen for a week to emo rap, I get emo rap recommended in the next one.
I think song/album radio is not exactly based on your taste, but on what spotify considers similar.
Try making a playlist with your favorite songs and press "enhance" or "playlist radio" to see recommendations based on that context.