Maybe I'm missing something but iTunes doesn't work like that. The iTMS does give you links to all the music but only to sell it to you. My Library however is useless for clicks/links etc, I've been using iTunes since the day it was launched and I've outgrown it/it hasn't grown up.
I'm genuinely not trying to attack you or anything, so please bear with me. The iTunes Store does work like I described. You can access a discography page for an artist by clicking on the artist name. It has biography information and links to similar music just like Spotify has on the artist pages.
The latest iTunes version has improved links to the store from your own library. Just click on the name of the song, album or artist.
Of course iTunes only sells to own, I know that. but all the functionality to stream and to compete with Spotify is already there. Already now you can listen to streaming parts of each song (1.5 minutes per song) and you can even queue songs that way to play sequentially.
So, like I said before, everything is in place. Save for a favorites (or star like Spotify) function to mark your favorite songs.
I use Spotify daily because I like the possibility of listening to songs I don't own. I'm frustrated that Spotify doesn't have older music from popular artists and that it is polluted by many amateur copy artists. iTunes will be better in that respect.
I'm running an iPhone 5 and it takes 30-120 seconds for my purchase list. Then it loads extremely slow while scrolling. Purchases won't even load on either of my 2 iPhone 4. The App Store crashes. (iOS 6.0.1)
I tried to hide purchases to try to help but the feature isn't working (swipe right in list to reveal hide button). I hardly ever get on iTunes on a computer. It's worth a try if you want to speed up loading of purchases though. You can always find previously purchased content searching iTunes to reload without additional cost.
I can see that that must be frustrating, but it seems like this is an isolated problem with your device. I would suggest making an appointment with a Genius Bar.