wouldn´t it be better to test all lenses on a, lets say 180MP medium format sensor?
But what would the outcome of that test really be? Why do I need to know that my Canon lens resolves better than a Nikon equivalent at 180mp? Is there a 180mp on the market, or even the possibility of one?
I get what you are going for, but, the result would be so far divorced from reality that it wouldn't really be useful. I mean, even DXO's sensor tests are a little out there, because they are just testing the sensor, not the electronics that deliver the actual image. But at least it's mostly grounded in reality; it's a sensor that exists. And when they test lens/camera combos, they are things I could use in the real world.
Would knowing that the Nikon can resolve a tiny bit better on your 180mp sensor make me change from Canon to Nikon? No, because today, on the cameras they both have, there is no noticeable difference. And I'm taking pictures today. The results would basically just be fodder for useless flame wars.