Novak isn’t done yet. Wasn’t it Monfils, Nishkori.
Be incredible if he nabs 25.
I think you are missing the point completely.
Firstly, I haven’t even mentioned Novak but since you brought him up, he does have a few years left in him of winning Grand Slams. I’d say 3-4 maximum. Not going to be playing the same at 39 and I do see 25 Grand Slams for him as likely.
Secondly, you are comparing young talent to players (Monfils and Nishikori) similar to Novak’s age who have not made it. Unsure of others views of Monfils and Nishikori but I personally never rated them highly. It was clear that Novak and Nadal would be the standouts of their age group.