My understanding of the experimental design is that they tested for a stationary, luminiferous, light propagating, non-interacting with mass, uniform, ubiquitous medium.
This is but one possible definition of a medium. The medium could also be defined as non-stationary. Or as a substance that interacts with mass. Or that varies in different regions of space.
The interferometer experiment was ingenious. But it had limited detection sensitivity for a very specifically defined medium, when other definitions are possible.
As a practical example, if we suspected a medium that interacts with matter, the experiment fails even if the medium exists. Ex. The Sun would physically interact with the medium, the Sun's angular momentum would transfer to the medium, which would subsequently transfer to the Earth. The Earth would be in near lockstep with a rotating medium. The M/M experiment would not detect such a medium, as there would be no Doppler shift to detect.
So, why are the Michelson-Morley experimental results interpreted more broadly than the scope of the tested medium? Why is the experiment held up as evidence that NO medium exists, instead of the more accurate statement, that the exact medium defined in the M/M experiment wasn't detected, but others are possible?
If someone feels moved to say I'm right, but that subsequent findings by Einstein and Eddington removed the need, they are separate considerations. Why is the interpretation of the experimental results extended to all possible mediums, rather than what was tested for only?
This is my first post here, so please be kind!