I'm surprised this thread got to 8 pages. Having only read first few pages and skipping to last, it doesn't seem to me that much has been defined. And, I certainly have no real world understanding of the culture and ambiance of UK golf clubs, having never been...
I assume the consensus is generally with the maxim, 'when in Rome...' It seems to me that those of us that have a much less formal inclination when it comes to dress code and clubhouse protocols, are generally guests. And, if you are invited to play at a club with more rigorous traditions of dress and manner, you can either respect the invitation and comply, or don't go. Simple enough, it seems to me.
But on the question of whether traditions, and clubhouse rules, etc. are killing the clubs, I don't really think so. I think that some of the most rigorous clubs with what many of us might think are over-the-top traditions and rules, are clubs that don't really give a darn, and have all the members of the same sensibilities that they want. Stodgy old clubs of the parodied club David Feherty makes fun of "Scrotswoods" are an anachronism, that eventually the most musty and ridged of traditions eventually fade away, like most all anachronistic style. We don't see the old writing prose and vernacular of the great old writers of the turn of the last century, with their turn of phrases, etc. And, we won't see some of the stodginess of some of the most ridgid examples now either as new decades and culture changes.
But, it is all about choice. Personally, I don't care how prestigious it is thought of and how good the golf course is, I wouldn't be at Muirfield playing a 9 hole loop, go change for lunch to slurp some soup and make a show of eating a sandwich, then rechange to go our to play another nine holes, and come back to dress formal for a dinner. It just ain't me. But, they don't seem to be victims of a killing of their club, and I'm not dying to take part. Fair dinkum as those Aussies say.
And, for the record, there isn't a tinkers chance that I'd pine to play a course that requires knee high dark socks with one's bermuda shorts. I'm positive I can fill out my dance card of seeking out good golf architecture examples to play and still skip that embarrassment.
BTW, I have a question for my more well traveled foreign golf architecture seeking friends like Bill McB and Mike W. Having seen your photos at dinners after rounds at some to the greatly thought of international clubs, you gents being all dressed up in your sport coats and ties at the club house after-golf gatherings; I'm puzzled by the logistics of the whole process. Do you dress in coat and tie, on your way to the club you've been invited to, carry your golf clothes with you and change, then afterwards change into the coat and tie again- or the other way around, drive in golf attire, play and change in the coat and tie you carry with you? It seems to me to be an awful lot of extra baggage space to pack a coat and shirt-tie and enough golf and casual tourist clothes, on a typical multi-day, or week+ foreign trip, and your golf clubs to lug around as well.