Patrick,
Hmm, if the newer high end clubs are doing better than the iconic ones, that might say something else entirely! As in, doom the restoration market. May as well blow up those old things and try to match the new fangled designs if they sell more memberships!
I do agree that high quality is the key in high end, and may even be true to lesser degrees all across the spectrum.
Still, not every course can be either top 100, nationally recognized, or iconic with a tournament history in deciding what it needs to do in its coruse design.
But, as you say, and to address the original question, anything you do to make it hard for the pro makes it about 4X harder for the average Joe. No doubt that gap has widened. Just based on what is even harder for the average player, I would say favoring accuacy over length, and favoring finess (chipping areas) over power (rough and sand bunkers) probably does the best job of equalizing the field in terms of allowing most to play.
Those are still challenging for the pros, and of course, you can always grow rough for tournaments. But even light rough affects spin, reducing control, while allowing average players a chance to reasonably escape without just hacking it out.
Just some initial thoughts.