Dude, if you're not going to read what I am writing then there is no real point in discussing it.
Sampras played in an era when one surface was highly suited to his game (grass) two less so, and a fourth completely hostile to it (clay). Nowadays all surfaces pretty much suit all players. There are some differences but they are pretty minimal by comparison. Additionally the nature of the modern game (defensive-oriented) discourages upsets. It's a much better situation to be the top player in.
It doesn't take a rocket scientist to work out that if you were the Tour's dominant player for a year in the 80s or 90s, you were a contender for less titles in that period than if you are the Tour's dominant player for a year in the 2010s. That is going to result in the top players accumulating more slams.
I am not sure what is so difficult to understand about that.
The problem which you fail to see is that you build your whole case on mere three players, one of which would 100% dominate in any era, other would 100% dominate clay in any era and very likely be in a good chance to get a slam or two on other surfaces. You only have some semblance of a case with Djokovic, but even he is currently at his very best on slow and medium fast HC, and not on grass.
If everything suits everyone why Murray doesn't have a single finals on clay, let alone a title? Why Nadal hasn't won a title outside clay in a long time?