NOTE: This was originally released as a single post, but has since been split into three parts and expanded to better communicate my analysis and suggestions.
Theme park MMOs are all about the attractions. Dungeons, raids, open world, even PvP arenas are considered small pieces of the overall park. And just like real life theme parks, the attractions steadily lose their luster as time goes by, the newness fading into a sense of staleness.
Why this is can be traced to three particular elements, which when combined inevitably create staleness for the vast majority of the player base. Below, I trace these elements as they apply to the game Guild Wars 2, but the principles hold for any theme park MMO, even the behemoth World of WarCraft.