I cant wait for the big 3 retire, but lets go.
I think all these opinion saying djokovic is the goat, has to do with the fact that, now (2020), he is the best and most difficult player to beat.
But this is the same story when people said in late 00s that Federer was the goat. And then, by 2013 more or less, that nadal was the goat.
We have always the latest impressions on our minds.
Djokovic will benefit, in this "criteria", because he is the younger and have the bigger chance to left the last impression of the 3.
Federer have a big difference of age in relation to Nadal, and then Djokovic. Thats, for me, explain why he was considered the best for more time than the others.
Nadal is in the middle, but not much older than djokovic. Thats why Nadal was considered the goat for less time.
And now djokovic is here to take.
But he is still 2 and 3 slams behind their rivals. And nadal is more likely to improve this number than Federer.
When all its over, we will have to see the big picture, doesnt matter if Federer beated baghdatis, or nadal beated Anderson.
For me, Nadal had the toughest era. He played peak Federer when young, and played peak nole when "older". And still got 19, despite being the most injured.
Doesnt matter if the majority was on Clay, because the slams are unbalanced with 2 hards, 1 grass and 1 Clay. Even more unbalanced if you think its 3 fast and 1 slow. And he beated both players in in-form period on fast surface slams.
At least, Djokovic can hold the opportunity to win slams in a new transitional era. Nadal didnt have that opportunity and wont have that.
I think Djokovic won-slams draws were the hardest, though.
But, how long will take for tsitsipas, Medvedev, thiem, auger aliassime, sinner, to finally start their era?
The transitional era that Djokovic can take advantage, might not be too long.
Just like Nadal learned to play Federer, and Djokovic learned to play nadal, players (some) will learn to play djokovic now, and try to take advantage on age (stamina) difference.
Ivanisevic is a vital piece now on Djokovic team, because serve will become vital for djokovic if he is aspiring to get to 21 or more.