I understand where Duncan is coming from with his various examples, amusing they are too, as there are quite a few 'traditions' as he calls them that that are off-putting, not just to potential members but to those who've been members of private members golf clubs for decades. Very slowly the 'traditions' are dropping away though, although admittedly, pace is very slowly.
And Mark is right about folk turning up for weddings in jeans and sweatshirts. We have wedding receptions and christenings at my club and there is always a wry look on members faces when they see folks attire when they arrive for these functions - less of the wry look, more one of alarm though, when they see ladies in high heels on the putting green or kids splashing around in the 18th hole bunkers when players are attempting to play their approach shots, but's that's another story for another day!
To me it's primarily the economy and being busy with other priorities that keeps the younger generation away from golf and golf clubs, the latter has always been the case, the former a bit more so in recent years. I don't see the traditions of the game/club or the dress code or the parking spaces or the 'Mr Captain' approach, as being major reasons for folk not joining clubs, although admittedly none of them help.
Some of the things that appeal to me, and I believe others, about the game are the traditions, the history, the etiquette, the sense of peace/quiet/serenity/tranquillity and the standards, and as standards in society slip, progress some may call it, one of the last places where standards are seemingly important is the traditional UK golf club.
As Philip very nicely says "There is room enough in the golf world for the sort of club you describe and other clubs that are more traditional and thank goodness for the variety."
All the best.