You could actually make the counter arguement that the fact that four guys from the same era have aheived this feat and so regularly generally contest semi finals suggests that there is a distinct lacking in quality depth outside the top 4. and that other eras had much more real depth meaning the top 3 or 4 guys couldn't dominate so much. All statistically it really says is that the top 4 from this period have been very much better in Slams than the rest.
In truth ( taking my pedant hat off and considering the actual players ) I do think that while there may be a slight element of truth in that, yes it is very much more to with the players at the top being quite exceptional and Andy has indeed been very unlucky to be around at thi time re his prospects for winning Slams.
I don't deny the argument about lack of depth but as you point out the fact that there are 3 AMAZING players all playing at the same time is tough for Andy. We have had few one slam wonders in the last decade. Most of them. Johansson, Gaudio, Ferrero Costa, etc. came at a time just after Sampras/Agassi era and before the current crop.
Would you say there is a huge amount of depth in the women's game just because there seem to be different winners at every slam in last couple of years? To me this feels like the 2002-4 period of mens tennis.
No I wouldn't. While again one could argue that the bare facts could indeed mean a huge amount of deepth, I would agree with you that it is actually to do with a lack of significant figures right at the top oif the game.
And again, I do agree with you that the main thing in the men's game is the "AMAZING" players at the top of it.