Then you agree with Barnes's point. You can criticize him for leaving out the fact that Nasty didn't have Djokovic's modern advantages, but the point of Barnes' article was that over time, the definition of tennis greatness has itself evolved into something much greater and more elite than it was when Nasty defined it. You said, in an earlier post, "it's tempting to say that the more technologically advanced human civilizations get, the better they are, but that doesn't factor in a number of other variables and considerations", but you have to concede that tennis greatness, defined by the top player of a given era, is a moving target that has gotten more elite relative to itself in earlier eras. Either that, it seems to me, or you have to suggest that Nasty might beat Djokovic in that series. And I think I was as fair to Nasty as I possibly could be, short of giving him a crowbar to kneecap Djokovic on the way out to the court.
Now, on the other hand, supporting your argument about "variables and conditions" -- one time back in the 1990s NBC hired Magic Johnson to talk during their NBA games, and at one point someone asked him if the Jordan/Pippen/Rodman et al. Bulls, in other words, the best team of the era that followed Magic's Showtime Lakers, would beat that Lakers team in a series. Magic was effusive in his praise of the Bulls, but scoffed at the notion that the Lakers would lose to them. "Who's going to stop Kareem?" and so forth. This gets to the variables and conditions argument, because by that time there had been a bunch of new expansion teams and the league's talent had been watered down considerably. But hoops thinking on defense and 3 point shooting had advanced, and continues to do so. If those Lakers played today they wouldn't be shooting so many long 2 pointers, they'd be a lot more worried about transition defense, and several of them would be permanently parked behind the arc. They would play differently.
There's always a powerful incentive for upstarts to tear down the establishment. Analyze it, find weaknesses, and exploit them. Lendl was great, but if you can hit a lot harder than he does...Sampras was great, but not fast. If you can outrun him, keep the point going...Federer was great, but if you can make the match more physical than he likes...