"Fit and Finish is what most people who are used to the guns a few decades ago expect....gorgeous finishes, manufacturing tolerances so close you'd think it was a single piece, amazing wood selection, etc."
Well first, the good trees have mostly been cut down. You might as well try to find enough live chestnut to build a split rail fence and a barn.
What are you thinking of, Registered Magnums and Pythons? National Match .45s from before WWII?
A few decades ago S&W and Colt really made some crap. We're talking the '70s and '80s, right? I know the major makers made some junk in the '60s - think about Winchester's post-1964 fiascos when they redesigned everything. Maybe it worked, but it was an ugly and cheap move.
I've been shooting since the '50s and they made plenty of trash back then too. You simply cannot focus on the best of the best and ignore the millions of H&R guns, the millions of Iver Johnson guns and the long guns made by Crescent for just about every hardware store in the country. My father had one, an Essex 16 ga. SxS, back before WWII and it was shot loose in the matter of a handful of years (5 I think, but I could ask him if it matters, he's still alive) and sold off for next to nothing by his brother after WWII started.
The beautiful old guns that we see today are just the suvivors. In 50 or 100 years they'll be talking about guns from Brown, Wilson, USFA and all the expensive favorites from the custom builders.