Perhaps all the usual suspects... he hasn't specified. Regardless of the mode of reproduction, the inherent problem with color negs per se is that they're like having power steering on a narrow road.
A little too much tweak this way or that, and you're off the road entirely! To use another analogy, it's
like someone tone deaf who keeps singing louder and louder, even though they can't hit the right pitch
or properly differentiate the respective notes to begin with. By merely saturating (so easy nowadays it
seems), yet being unaware of how this affects the nuances of the gamut, all the related subtlety in the
hues gets blocked together, and the power of the color realtionships is killed. Sometimes less is more.
This should not be confused with the concept of contrast per se. I can work with either soft or highly
saturated hues, and still retain a very clean range of distinctions between similar hues. But how one
goes about this is somewhat different when printing color negs versus chromes. The problem is not
really one of analog versus digital reproduction at all, but more about how the ubiquity of the very low
common denomintor of the web has created a generation which is almost color-illiterate.