I enjoy your posts MG and find myself agreeing with you 99% of the time however I just can’t for the life of me see how you’ve come to this conclusion.
Everytime I’ve seen him play he screams premier league to me.
The last 2 years he’s looked the best centre half on the pitch, including VVD when they’ve played Liverpool. They’ve matched up again each other directly in both boxes for set pieces and Koulibaly easily had the upper hand to me.
Maybe you’ve seen more of him than me but I personally don't have any concerns of him not working here if he came.