When did you rate these players to be world class? I don't remember any top teams fighting over their signature at any point. I don't remember anyone including them in the list of great midfielders in any context, PL or European. Do you mean you personally rated them world class? If so, I respect that as that's your opinion, but if you mean it was some general consensus built over many years of performances, I am going to have to disagree with that.
As for your second point, again, Gravenberch was used as an example of why Liverpool are lacking this summer. He had the same tag as De Ligt and Mazraoui of a talented player who can't be any good if a team like Bayern are selling him and he showed nothing last year to prove that wrong. Mac Allister was the lesser desired option at Brighton's midfield and Szoboszlai had a very average profile and reputation before their transfers. So again, my question is do you mean they have players "performing" better or are we saying they are categorically better players and Liverpool saw something nobody else did at the time of transfer?