Different people, different taste. Would be sad if every game had realistic graphic, it would get boring. I don't recall Vindi being particulatly popular either, isn't the most played F2P game Maplestory and most popular P2P WoW. In anycase, their other game mentionned in the post has more ''realistic'' graphics.
I don't think the graphics are the weak point of this game, that's just an artistic choice. The part about there only being 3 classes is the one that turns me off

very little freedom, unless they're highly customizable, but I doubt that.