The easiest explanation is that this kind of combat has been done so much in the massively-multiplayer variant of RPGs that people are not really all that enchanted with it anymore. People come for the content, but stay for the people. However, western developers only pushed the combat ever slightly forward because they hinged the success of their games far too much on that fact. When Yoshida and Co undertook the task of updating their MMORPG (and they've done a great job at that), they looked heavily at western and korean MMORPGs who had been stuck in the evolutionary malaise of the last decade.

They don't need to be revolutionary innovators. All they need to do is handle the problems that should have been dealt with no later than half a decade ago and people would be kissing their boots and calling them god.