Due to my hobby I hang out with mechanically inclined men aged ~30-70. I have heard them praise all manner of things from years past. If there's one thing they agree has pretty much constantly gotten better with no regressions along the way it's automotive lubricants, at least up until the point where they took the zinc out of motor oil. Now, I suspect there definitely are some regressions, but they're definitely small enough to get lost.
I don't know how good whale oil transmission fluid actually was btw, I didn't experience the transition.
I remember older people talking about how much better it was. But like most times when people talk about how much better something used to be, I assume it was mostly not as good as they remember it.
But even 70 year old today would have been only 20 years old in 1973 when whale oil was banned, so likely they would have had only very few years of experience if any of using whale oil
