Newer digital sensors can resolve a higher 'resolution' than 35mm film. Using an older lens with a camera sporting a 20+ MP sensor will give you less sharp res

Newer digital sensors can resolve a higher 'resolution' than 35mm film. Using an older lens with a camera sporting a 20+ MP sensor will give you less sharp results than a similar new lens. But the image will be no worse than that old lens shooting film. And the lens will be much cheaper! If you (or others) like the results, the technical details do not matter.