Well, it's an awesome game. I have 180+ hours on 1 account alone.
Everyone else is expecing a story line RPG, which it isn't. You get to fight in arena combat to gain skills/levels. Go on missions with other people, join guilds, fight in the Hall of Hero's, fight in guild battle's, fight for prestige and just run around and fight things by yourself.
The level 20 cap is there because soon enough, the game will have an expansion and open up new worlds and new things to do. You can still gain skill points after you reach 20, but you don't level up.
Poison...I don't think you get the meaning of this game at all, nor Yon. However it's all opinion I guess.