I agree that we should distinguish quantity and quality. If we don't have enough light in a scene, we need to raise ISO for a given camera and that can easily

I agree that we should distinguish quantity and quality. If we don't have enough light in a scene, we need to raise ISO for a given camera and that can easily make scene look bad. For other camera with bigger and less noisier sensor, brighter lens there can be enough light and it can look very good. I can imagine that there are cases, where increasing amount of light will only improve picture for a cheap camera. If the light is plentiful and bad, cheap camera can produce abysmal results with parts of the image completely washed white in one part, and very dark in other parts. Good sensor with high dynamic range will produce much better results. Of course, improving the light will improve both results.