>>47606642XY is about being able to see the good in people and not judge them by their short comings only (the mistake which Lysandre and AZ before him make). The ghost is here to tell you the same thing, but about yourself : you're not perfect either, nor even exceptional, however that's okay both for you and others and the game will try to teach you that.
Same point as putting Zygarde in Terminus Cave (terminus as in the end of the journey) : figuratively, if your view of what makes someone good is able to withstand you not being the savior of humanity (since Zygarde is supposed to show up when the world is in danger, and it didn't during your adventure) you've passed the final test and managed to understand what the game wants to tell you.
