The masked carnivale is fun. Doing log duties and weeklies as a blue mage is fun. Doing old raids and achievement extremes on blue mage is fun. Learning spells can be fun because you can do it in different ways or solo them.

Raiding on a blue mage might actually be more interesting than on normal jobs because you get to bring different abilities depending on preference or the strategy you want to use. We don't have that variable normally. The healers get to have more attacks than real healers and the tanks have to work harder than normal tanks.