It's true that as film containers, interchangeable lens film cameras has little effect in image quality. Even then, the lens was never the sole factor, and film emulsions did advance over time. That advance was slow compared with the first couple of decades of digital sensor development, so the old "a good lens is always a good lens and an investment" claim is less convincing now - otherwise we wouldn't see so many revisions of the 70-200. Sensor advances do seem too be slowing as the technology matured, though. But a bad lens is still a bad lens!