The story is FFVI is not silly at all. While not blessed with a great dialog (technical limits on the translation and the translation itself being wonky) the plot and themes raised by it are classic and very sound. It's simply told, but more effective for it.
The sharing of hardships, of carrying on and healing through understanding and acceptance is a universal idea. The different characters all have doubts, demons in their past, or failings they are seeking to change. That they do so and find peace in a world (and thus universe) that seems arbitrary, again reflects the "real world".
Kefka is the dark reflection of that. An uncaring, self interested person to the point of being a sociopath, attaining more power and control is his only aim. Once attains supreme power, he finds it doesn't fill the void in his existence, doesn't make him feel greater or more content. So, he makes the conclusion that if one has mastery over themselves and their environment and still feels no purpose or place, existence itself must be a con, a worthless thing, and should be wiped out.
The other characters become better people and gain peace through their weakness and failings, through loss of power/control; Kefka becomes a complete nihilist despite gaining everything he wants.
Again, it's very simple and lacking in much nuance, but as a plot it's solid.
