"Thumbs Down" doesn't seem to be working on my 90's Radio channel

[Pilot1226]

Hi all,

So, I've been using Spotify (free) on-and-off since the launch in September, and about a month or two ago I decided to drop Pandora/IHR and use Spotify as my go-to radio app.

I'm a big fan of the 90's scene, alternative in particular, which includes artists like Incubus, Oasis, Blues Traveler, Dave Matthews Band, Stone Temple Pilots, Soundgarden, Nirvana, Foo Fighters, etc.

Because this is such a broad station - 90's music encompasses all music from the decade, I guess - I'm occasionally using the Thumbs Down for certain songs.  Don't get me wrong, sometimes I'm in the mood for some Hip Hop, but I just don't understand why I hear like 5 or 6 songs in a row that I "Thumbs Down" and then have to change stations because I'm out of skips.

Example: I'll hear Collective Soul, Train, Barenaked Ladies, Dave Matthews Band, Tom Petty, Oasis (which I all consider relatively similar styled alternative), and then I get Notorious BIG.  I'll thumbs-down it, and get Puff Daddy. Thumbs Down again, and I get NSYNC. Thumbs Down again, and New Kids on the Block come up. Thumbs Down again, and then I get Tupac. Don't get me wrong, I'm not opposed to hip-hop/rap, I just would prefer this to be in the hip-hop station instead of in the 90's one that I'm tailoring more towards 90's Alternative/Grunge.

This usually continues until I'm out of skips, and then I change to another station.

Usually some time will pass, a few hours, and then the next thing I know I've got C&C Dance Factory, Haddaway, Sir Mix-A-Lot, and LL Cool J on my radio again. Repeat the cycle over and over again. 

I'm trying to understand why if I'm thumbs-downing everything that ISN'T a Grunge/Alternative why they keep coming back. I don't think I've thumbs-upped any hiphop or rap on this station, so does anyone have any thoughts? 

EDIT:

I'm wondering if Spotify "releases" more tracks after you listen to a certain amount of the radio? For instance, the station lets you hear more popular songs for the first... "50" hours of streaming you hear, and then they'll release more deep-cuts, etc., the more you listen to it. That could explain why every couple of weeks I'm getting such weird songs considering my thumbs up/down.