This is one of if not the strongest era, where you have more than one player able to win a slam. You have three very solid players competing at the highest levels, battling it out in nearly every slam.
This can be said about every other 'eras'. There have never been an era when only one player was able to win slams.
And actually, in other eras, we had more than 2 or 3 players winning multiple slams, but in the last several years, we had not more than 2 or 3 real contenders at the slams, and everyone else was/is labeled as 'no chance'.