Should the highest rated active player be world champion?

 Title says it all

No. Whether you top the rankings depends on how often you play and whom you have played.  Deciding a world champion should depend on a competition to find the world champion.

A different but related question is whether the present system is a good one. If we go back before WWII the world champion more or less regarded the title as personal property. With the death of Alekhine that changed, but we are still left with a system where the title is decided by match which always involves the current champion playing a challenger. Apart from professional boxing, I know of no other activity that decides a world champion that way.

The world championship should be decided by a competition involving the best players. How you decide who takes part and what form the competition takes is open to debate.