I somewhat agree with the assertion that great golf clubs have a lot of very good players. However, I do not think that all clubs with high numbers of low-hcp players are necessarily "great golf clubs." Isn't there a relatively new club (I wanna say Phil Mickelson "designed" the course) which claims that 75% of it's members are 10 hcp or better? I want to say Whisper Rock in Scottsdale, but I'm not sure.
I think that many good players is a good addition to have if you want some prestige as a club. It gives modest publicity to the club, and legitimizes the golf course when an outsider sees how good the member is (that said, I've played with a couple members of prestigious clubs, and they haven't performed exceedingly well).
Here's an interesting question: Are there any "great golf clubs" whose courses might not be considered "great" on their own? I've played a couple that have had a great feel, despite less-than-great golf courses. The two that come to mind for me are Sharon CC in Sharon, CT and Lake Waramaug CC in New Preston, CT. Both short, old, quirky 9-hole courses, but in really nice settings. Modest and low-key, but very enjoyable. Of course I won't hesitate to say that the best pure golf club I've ever seen is Newport CC.