My guess is Kageyama is too predictable, then easy to read. So the blockers will continue to own him... until he starts being unpredictable again.
Probably comes from the fact his tossing choices are always striving for the optimal smash. The optimal smashes set is a lot smaller than the scoring smashes set. It also stripes smashers from showing how great they are, adapting to very hard to strike balls and growing in the process. His asumptions are probably too much on the safe side, not giving him and his team mates room for improvement and impredictability.