Without Indy, there would have been no USAC. Without Indy, there would have been no CART. Without Indy, there would have been no IRL. The more you try to diminish the Indianapolis 500, the more you try to diminish open wheel racing.
It is NOT still a split, IMO, between those who enjoy the "500" and those who enjoy other open-wheel races. It is a split between those who recognize the magnitude of the "500" and its importance and those who do not.