Look at Hardens numbers....they are 6 points better offensively with him on the court than they are without and the defense plays the same with or without.
Despite being the only guy on Houston that can create his own shot, he is still shooting 44%. And is a master at getting to the line. His PER was 23. last year and 20.6 this year. His effective FG% is 50%. He gets to the line, he rebounds, he sets up teammates. Heck even for a much shorter shooting guard, he rebounds better than Durant. And averages more assists.
Obviously, he's not as good as Durant, primarily bc he's not as good of a shooter.