The humongous difference, then, are the chiefs and the mechanics who made all those cars that looked the same and those engines that were badged the same, perform so much more individually different.
One thing I'm noticing totally different in fan talk on this forum and the atmosphere of Indy car racing I grew up in is the props for the guys who make the cars go fast; the Porters, the Beckleys, the Watsons, the Phillips', the Learys, the Capels', etc, etc, etc. Compare that non-issue due to the political rule making in Indy car racing today to the status of the wrenches in Sprint Cup and how their stories add-in to NASCAR's large appeal.
The wrenches in Indy car racing used to be as almost as popular as the drivers to Indy car fans; that invaluable asset to the sport practically doesn't exist today. The way to begin renewing that great input is to first put the engines back into the teams' hands.