This character system is awesome cause you can make your personal party.
e.g. If you want Fironiel to be a paladin he can be, if you want to stop all the stereotypes and make Maria a tank go for it!
I think the the only reason people bash it is because it takes a little extra work and planning to achieve making a good party.
In Most other Final Fantasies it is set so the thief is made obvious also the warrior, the mage(s), the tank.