Greater number of players achieving higher slam counts than in the past.
This argument is extremely flawed. What makes you think that you can determine how a high slam count was achieved? Are you going to ignore factors such as TALENT and COMPETITION? Or are you just going to attribute it to surface homogeneity for the people you don't like? Is there some objective indicator of slam merit that you're going to use to measure the worth of a slam?
Player X: "I like his game! He is extremely talented! He will go on to win many more slams! They're all 100% legit!"
Player Y: "Oh, he's only winning because of the slow surfaces! His slams are only worth 75%"
The U.S. Open used to be played on clay. So because of the surface change, do none of Fed's U.S. Opens count?