It sounds as if you really DIDN'T try Pandora? With Pandora, you can create your own "station" that you can customize with the songs that you like. Pandora will then "suggest" other songs that are similar to your likes and you can thumb up them or thumb down them. Apparently, you aren't aware of this feature?
I was using it to stream via BT when in the shower and driving in the car, there is no option to thumbs up/down in those situations as my phone is inaccessible. If Pandora depends on that to function correctly then it's not something that would fit my needs. I don’t actively listen to music in any other situations, as mentioned in my first post.
FYI I tried Slacker for a couple days in the same context and ran into the same issue. It would play a few songs I liked then it would start to drift into vey different music that I had no interest in.