Epicycles created a consistent framework in which to produce repeated measurements and observe anomalies. It was an agreement that this was the basis on which observations would be compared, which turned out to be encompassing of the minimal correct theory. I think that is how to view string theory.

The difference is Pareto efficiency on the (time,quality) axes. Circles and then epicycles were the best model ever known until superseded later by ellipses. String Theory is not the "latest and greatest" , it's latest and less good than it's predecessor, making it useless as physics.