Your reactions to things aren't typical of most people on the internet, Nario. You are an idealistic guy in a world of cynicism.
Really? When I joined and saw that I could level up, I thought that was so cool. I was immediately ready to figure out how to level up!
I personally kind of feel that the RPG system, while a cool idea, was needlessly complicated in the long run, and had a lot of aspects that discouraged new folks from joining and participating in the site.
I can't imagine that the level up system would be perceived as onerous by anyone, but having to write a review to score a song left a ton of songs with no scores. That was a big flaw imo.
The level up system was a fun idea, but it basically made it a game which means to make it both fun and good, it really needed a lot of testing and tweaking. That takes a lot of resources and time to do right (think of the way Valve makes a game) and can easily be botched badly (think of how mediocre or worse most games turn out to be).
As for achievements... that would be a lot of fun and it's been done in other places (the Escapist forums has something going). I wonder how that would work in implementation. At some point you need to take the relevant stats from the database for a user and determine if they met the criteria for an achievement and then award it. I wonder when you would do that.