The point is it's easier to rotate a dizzy cap by hand in a matter of seconds for however much horsepower/torque than it is to go out and buy a programmer for absurd amounts of cash and then fiddle around with it for an hour or so just to see a small gain.
I'm not saying a lot of them can't be outrun in stock form; I'd be lying if I claimed they could. Tech has come a long way; however its much simpler to coax horsepower out of an old pig engine than say a newer one, simply because newer ones are in a higher state of tune due to the ECU and modern EFI systems etc. This is especially true when it comes to smog-era vehicles; simply tinkering around with it and removing unneeded equipment will nearly double your horsepower. I bet if you took all that away and slapped a carburetor on a new 6 cylinder it would hardly have any better horsepower than one out of the 80s, at least when it comes to American cars. Hot Rod proved this when they built a carbureted Coyote 5.0. They dropped the ECU and injection, built a high end intake and slapped a 750 Holley DP on it and lost power over stock(at least initially before they opened it up). With new ones even after a remap you have to buy parts one after another just to start to make noticeable gains which are incredibly more expensive than say an older engine part would be. Its ultimately cheaper to make an old car fast than it is to buy a fast car new, at least from a certain standpoint. This is exactly why everyone loves Fox body's. You throw $3,500 at a Fox after purchase and you'll blow the doors off any modern N/A 5.0 and most new cars on the road for fraction of what it would have costed you to go out and buy even a V6 Mustang, any Accord, Camry or whatever modern "average" car you want to throw at it.