Okay, so I only read the first two posts under this thread and will disagree with almost all that was written.

"A few years ago, I concluded that a lot of the flies they tied would not be as effective these days. For three reasons:
1. The year after year; and increasing each year; fishing pressure on the streams and trout.
2. The application of "relatively" recent understanding of insects, their behavior, etc.
3. The development of new materials"

None of that has anything to do with trout reaction to potential food. Do you think trout pass on information to their proginy? Do you think trout learn in cemented hatcheries? Do you think even wild native or non-native trout know the difference between rabbit/muskrat/synthetic dubbing? What I have learned after 50+ years of fly fishing, speaking with other fly fishers, reading a lot about the subject, etc. is that we fly fishers tend to give trout a lot of credit and that, according to some of the masters you cited, trout have a tiny brain and are simply dumb as sh*t. They react to potential food for several reasons. A minor one is the specific fly pattern.

Hey Buddy - You write, "If Lee Wulff was here today, I doubt he'd be tying and fishing the same flies he fished during his era." Perhaps you should learn what flies Lee Wulff tyed and used before you make such a claim. If you were to see the last video of Lee Wulff, you would see him tye 5 flies ranging from one with very modern synthetic materials to his named Royal Wulff and down to a size 28 Grizzly Midge. Oh, and Byron he didn't use a vise or a bobbin. So I completely disagree that Wulff would not be fishing the flies of his era. He would because the fish and what motivates them to 'hit' flies has not changed. So although he'd likely try some of the modern flies and as an innovator he'd be tying some new fly patterns too, he'd be catching fish with his old 'stand-bys' as well as flies that have come around since his passing.
You guys might be interested in seeing a few of the 'underwater videos' in which trout take opportunistic food which may not be food at all.

Anyway, you're entitled to your opinions.

Allan