Does it really take "decades" to learn how to pedal smoothly and spin - ? I'm 64 and I wonder if I have enough time left to develop Souplesse ?

Your estimate of over 50 mph exchanges (especially on a small track) is also a touch exaggerated, IMHO.

BITD a smooth high cadence was more important because of the larger jumps on the 5 speed freewheels and not being able to shift under a heavy pedal load. With the crappy shallow shoe cleats of the day you would pull out of your pedal if you tried to "muscle" the pedals around.

Nowadays when I see a rider flailing away in too low of a gear I sorta feel sorry for them.

There's a lot more to riding than smooth extremely high cadences. This is 2025, not 1965. Like a lot of things it doesn't hurt to have that ability, but it's about as useful as having a smooth graceful step-up to mount your high-wheeler.