Makes you wonder how many players in eras past had a cig before a big match.
What the OP fails to realise is that yes, tennis is a much more brutal sport today than it was 50 years ago. But it's more brutal today because of the advancements in technology. Better racquets, better training methods, better recovery methods, better diets, better footwear, better IP in just about every facet of the game. Plus, tennis did not always have sit downs at the change of ends. Tennis did not always have tiebreaks at 6-6 of a set to bring it to a premature close. Give Laver that sort of technology and groom him for today's era and then you would see a more brutal version of himself. He would still probably have that Popeye forearm and he would still have that tennis ability, but he would have all the other stuff that goes with being a top player today.
Each generation learns from the previous generation. Next the OP will talk about how office secretaries are so much better today because they have Microsft computers yet the secretary from yesteryear only had typewriters.
OP, I'm afraid you're comparing apples with oranges.
That is all.