I agree that wrong is difficult to define in these contexts, but remember that the only proof of the existence of the ether was that 1) light was thought to be

I agree that wrong is difficult to define in these contexts, but remember that the only proof of the existence of the ether was that 1) light was thought to be a wave by the mathematical formulation of Maxwell, and 2) all known waves had a physical medium. That's it. It was a very ad hoc construction that immediately presented ways to test it. When it was tested by the MM experiment, it turned out to be undetectable at best, thereby exposing its weakness as a theory. Einstein didn't use the theory as a springboard because it was so good and useful; he used it as a springboard because it was so bad.