On the right >>>, you have a list of quests and the one with a fireball icon is the Main Scenario Quest.

On the left <<<, you have the Scenario Guide. This was created in case someone messed up their quest list, did not pickup a quest, or hid the quest, to help new players (I personally disable it).

People used to ignore their Job Quests sometimes, which unlock new attacks, so they incorporated that into the Scenario Guide to help guide new players to do those as well. It does seem an oversight that it doesn't check you progressed MSQ enough though.

This is another example of what I always say though: MSQ gates new areas and its associated content.