It's on topic. One of the differences between old and new zooms is in-camera sharpening and other tweaks. That makes it more difficult to tell what's lens definition and what is processing. Canon EOS is one of the few brands that has a lens range to fit both film and digital cameras natively, so direct comparisons can be made.
I got your point. I did not even think of concerning a lens quality based on looking at photos taken with such lens mounted an a digital camera.
I thought of either comparing MTFs, or, still better, of comparing old an new lenses mounted on a film camera.