Blue Mage, which you listed as an example, is quite literally just side content, a mini-game. It's main function is The Masked Carnivale.
It's about as parasitic as the Golden Saucer.

Deep Dungeon, also a mini-game... Complete with leaderboards too.

Now, places like Eureka and Bozja are closer to parasitic content. As stated by others, it is still completely optional.


The biggest problem with the parasitic content in games like WoW is that it is 100% necessary to participate in said content as they lock in certain bits of gear into the systems.