In World of Warcraft, the shared world is where you complete the leveling game. It is organized by and dominated by quests. The goal of the leveling game is to earn experience points and to complete it as time-efficiently as possible. The end game is the real game, and it takes place in instances. The goal is to improve your gearscore. Completing achievements and collecting pets and mounts are shared mini-games between the two levels of play.
Or at least that is how I see the majority of hardcore players. If you disagree, the question is not whether it is true for you but whether you think I have mis-assessed the majority. You could also make the case that the real majority is casually making its way through the leveling game. Those people are less likely to be engaged in MMO blogs or the meta-game, so I don’t know if they are part of the conversation.
In City of Heroes and The Lord of the Rings Online™, the leveling game is the game. There is a veneer of end game, but people who think that the game begins at the level cap are severely disappointed. There is some harder content at the cap, along with the chance to farm for best-in-slot gear, but the games are designed for the journey. If you power-level to get past the leveling game, you are just missing the game. The end game is pretty much more of the leveling game, without experience points. (Completing badges/deeds and collecting costumes/mounts are shared mini-games between the two levels of play.)
Going from the latter two to the former, I was constantly annoyed by “the game begins at 80.” Meanwhile, the population in the former is much larger and therefore is a constant source of complaints as visitors in the latter two. “I left WoW because I was bored, but this game sucks because it isn’t more like WoW. I need you to change it for me now, because I’m going back to WoW when the next expansion drops.”