If in-fact someone spent the time and/or resources to create all the content that people could possibly want before an MMO was released, that MMO would become the Duke Nukem Forever of the genre. And even if that MMO was released it would still be years behind the other MMOs that had been constantly releasing content while our theoretical MMO was still being developed. Are you following? Any new MMO is always going to be behind older MMOs due to the dynamic nature of this type of game.
Players imaginations and expectations always exceed reality.