If you were to say any a player from any other position was the best in the league then they would be most likely considered to be world class why is it different for defenders? You could say the league isn't as good and someone else case say attackers are now better than the past, it's a bit of a chicken and egg argument tbh.
Ramos is incredibly overrated, yes he scores a lot of goals but he's a defender first and foremost.
If we're talking about defensive ability I'm taking Kos all day, Ramos is a calamity and gets away with murder in La Liga. He really isn't a great defender.