Has a lot of old school hot rodding been lost?

A lot of "old school" hot-rodding has been replaced by the aftermarket. In the late '40s, if you wanted to go fast you put a flathead anything in a lightweight body, then started throwing out anything unnecessary. If you needed more airflow, you added another Stromberg, usually on a fabbed manifold, and built your own exhaust manifolds/headers. Cams were regrinds and almost always experimental to some degree. Then Vic started casting manifolds, and Doug Thorley and Hooker started making headers, while folks knowledgeable in cam timing like Ed Iskendarian started making new camshafts. Various manufacturers stepped up with pistons. The OEs started making huge (for the time) 2- and 4-barrel carbs, which quickly found their way into old-school cars, along with better OHV engines... and the aftermarket came along to support those, too. Have you ever seen Ardun heads? "Let's apply Chrysler's Hemi engineering to a Ford flathead." With rare exception, virtually every viable aftermarket "gee-whiz" carburetor we use today is a direct descendent of a production-line part--even the Dominator. Hell, by the 1960s the aftermarket was strong enough to have eliminated a lot of "traditional" hot rodding. Very few, if any, bought a '66 anything and said, "I'm-a stick-weld up some headers for this bad boy."
There are still guys doing it, though, and it's made a resurgence. A good friend has a legit old-school hot rod: 1931 Ford A with a '37-ish flathead V8. It's got '38 (I think) hydraulic brakes, dual 97s on an old-school "tunnel ram", straight "lakes" headers, and artillery wheels. Gears are, I think, 4.44:1, and the transmission is a truck 3-speed ('37 or '38). I can't think of a post-1950 part on it, although it's been converted to 12V (still a generator, though). In 1947, it would've been a world-beater. Today, nobody would call it fast, including him. Cars like his didn't exist when we were kids, even at shows.

If you're a huge fan of truly old-school hot rodding, you should attend the Symco Weekender (formerly the Symco Shakedown) in WI. They do not allow post-1964 cars, nor cars with post-1964 parts visible. No EFI, no modern wheels/tires, no billet anything. They don't even want open hoods (it distracts from the car's lines). If you don't meet the criteria, though, they have VIP parking--which is a car show unto itself. The show rules are worth reading--more shows should be like theirs.