The problem is that people still compare him to old-school CBs like Terry, Ferdinand, Alex etc. and don't get that even defenders change, especially when you play with a high line defense. The defenders' duties are not longer just blocking shots, tackling and heading, they also have to be able show mobility, good passing and good ball movement, and Luiz is one of the most modern CBs nowadays. He has it all except for experience but he'll keep improving.