I think mostly that all illustrates the point that we are all different. Pretty deep thinking, eh?
But I find that I really value stability in a bike. Even as a young criterium racer I wanted a stable bike that I could ignore if I wanted to. I took some rides on the aggressive "crit" bikes of the day and hated them, because they were so squirrely. I did once manage to build a frame that was too stable - it "plowed a furrow" and I had to force it to do anything but go straight, which was surprisingly disconcerting. That was a pretty extreme case, though, and interestingly enough, was greatly improved by fitting narrower tires run at higher pressure. At any rate, the truly low trail bikes that Jan says are perfection on two wheels are unpleasant to me. I have a harder time riding no-hands with those bikes than I do with "standard" trail bikes fitted with handlebar bags. C'est la vie.
The short version, I suppose, is that there is no such thing as one "perfect" geometry. I still am firmly of the opinion that "British" geometry perfected in the 1950s and 60s (73 parallel with two to two-and-a-half inches of rake) should be adequate for most people under most circumstances, but I wouldn't guarantee that, either.
I think you are absolutely correct when you note the issues with individual proportions and body weight. Most of my frames are built with 9/6/9 tubing, which is quite heavy, according to Jan. It is what I raced when I was 158 pounds, and I never felt that it was too stiff or flexible. And it also worked for me decades later, at 220 pounds, but capable of putting out far less power. When I built a bike with 8/5/8 (still heavier than Jan likes) I found that the handling was quite poor until I lost 50 pounds, at which point it performed perfectly. But any time I get beyond 190 pounds, it starts acting funny again, and I start preferring my 9/6/9 frames.
Which is all a long, drunken, rambling way of saying that I suspect it's possible to worry about all of it far too much. I really am to the point that I think Grant Petersen may have it all figured out when he says that he refuses to discuss geometry at all anymore. As long as we've got room for the tires we want to use, we should probably all shut up about it and just go for a ride.