I think you lot are being too literal. It doesn't much matter if 40, 50 or 60% of the top courses are modern. Considering how many modern courses there are, there is a strong suggestion that design hasn't improved. Modern design may (and I stress may) match classic design, but I think anybody would be hard pressed to say it is better. I don't much care about all the dopey reasons about poor sites, housing courses, profit making etc. Despite these limitations, I think it is well within the powers of archies to consistently design courses which are at least the equal of classic courses. There really isn't a good excuse as to why they can't. Therefore, the answer to Ted's question must be something about the modern aesthetic and emphasis of design.
I know from my PoV, carts are a big reason why courses today often come up short. The concept of carts effects site selection, design decisions, walkability etc etc. This is a question of design emphasis and I think it can be argued that often times the goal isn't to build the best course possible given the budgetary and other restraints. This could simply be due to, despite the high profile of some archies, a question of archies not being in control of their field. Once archies aren't calling the shots, architecture will generally suffer.
Ciao