Nadal was never the GOAT or even the greatest of the Open Era. He needs at least 3 more Slams than either Djokovic or Federer because of his significantly inferior resume in multiple barometers of excellence over his peers. If I wasn't being obvious with my previous sentence, Nadal lacks in absolute dominance over the field such as him having significantly fewer weeks at #1, having 0 titles at an event that requires facing top players in the Year End Championship event, having only one 3-Slam season compared to the other 2, and never defending titles on a surface other than clay until very, very recently. Federer at least has a few measures where he is ahead of Djokovic, such as having 5+ titles at 3 Grand Slams, leading in Year End Championship titles, and consistently making it to the semifinals at the Year End Championship event, but Djokovic has an overall more balanced resume as of now. Nadal is not just a little bit behind Djokovic and Federer but a considerable distance away.