"Lorentz ether theory" Raising ether theories is usually troublesome especially pre-Lorentz concepts such as the luminiferous ether but one can't deny the fact

"Lorentz ether theory" Raising ether theories is usually troublesome especially pre-Lorentz concepts such as the luminiferous ether but one can't deny the fact that c = 1/√(ε0 μ0). If we agree that this relationship is accurate then it seems to me that that just saying the vacuum permittivity and permeability are universal constants is a bit of a cop-out. If ε0 or μ0 change then so does c. Whether one uses the word ether or some other, there's something about a vacuum that's very significant/determines the rate of causality, etc. Edit: seems to me if we had a better understanding of that relationship then we'd likely have an answer to the fine structure conundrum.