I think you're still missing the essential point. And you're still comparing players in a vacuum (unfair to past era players. There's a 9 year difference in ages between Sampras and Safrin. That was a huge difference then). We all know the "next generation" in any sport will likely introduce cutting edge techniques, many times play with more advanced equipment, and been reared under more effective training techniques, leaving the old guard to evolve or die, and they're usually too past their prime to really "evolve." The peculiar thing about today's tennis is where is the 20 year old Safrin on tour taking apart one of the old guard like he took Pete apart in that video? We're not even getting a hint of "the next generation." It's still the same old story every major.
There's no logical way to compare players across eras. You can't even say, "Well, I watched both [insert players] at 24, and player X is just far better," because player X will likely be a more current player who had training, knowledge, and equipment advantages player Y didn't. Basketball example. Is Curry a better player than Larry Bird in a vacuum? I think so. Do I think Curry becomes an all-time great if he were born in Bum , Indiana in the late 50s and learned to shoot in his driveway? No. The best way is just to rank by era. NBA has the Russell, Kareem, Magic/Bird, Jordan, Duncan, Lebron eras, for example.