The problem with having full customizability is that you basically never end up using over half the characters. Which mean they have no real attachment to your party outside of the occasional custscene in which they pop up.
How is saying they don't change a grey area? If they don't change they don't change.
You find out their story as they go along... that is still no excuse for them to not develop as charactrs throughout the entire game.
Yuffie. Once again you find out why she is who she is... but she doesn't change at all through the course of the game.
Here is a good example from FF6.
Take of all characters... Gau.
A wild anti-social beast boy... later in the game you find out Gau is who he is because he was abandoned at birth because his mom died in childbirth.
However, Gau changes during the coure of the story still... becoming more and more trusting and civilized... even so much as going through training to embrace his humanity which he once abadoned just as he was.
Or say... Shadow. You learn about Shadow as you go on and why he's an emotionless bastard... you even find out he had a daughter.
yet, you also learn he isn't as emotionless as he suggests, he does things for emotion as the story goes on and he learns to feel again. By the end of the story he is no longer a coward and an emotionless bastard but instead he has accepted his faults and ready to atone.
A lot of characters in FF6 are just more developed both backstory wise, and character development wise.
As for explaing Sephiroth... if you did... it wasn't in this thread. His reasons and motivations were just useless and stupid in general, let alone compared to Kefka's. Which were actually fairly philosophic, tied in with a bit of selfishness and narcisism.
You bash Kefka for having no motivation, when really Sephiroth is simply the one who went insane and wanted to destroy everything.
