This is probably true. I remember that many long time members of my guild started having performance issues during cataclysm and MOP. Complex rotations and complex mechanics seemed to be too much for them so they quit or got benched during progression and then quit. They started playing private servers after that, claiming that vanilla-wrath was when the game was truly difficult and that retail was for kids. I always wondered if they truly believed that or if it was a coping mechanism or delusion so that they wouldn't have to face reality.