I disagree with both of you, respectfully.
MT's game isn't anything like Hardens or Manu's. Try Jason Terry, Mayo or Jamal Crawford. Harden has AS talent as a SG/SF, and can break down defenses and get to the rim or create. Also pretty good defender. Manu does the same from the SG spot, where has been an AS multiple times. MT is a tweener scorer, who's far worse than either defensively, and doesn't have near the all around game. Those two create with the ball in their hands for themselves or others.
Also, those two can afford to come off the bench because the starting units are phenomenal on the defensive end. That gives them the luxury of bringing them off the bench. Recommending bringing Reke off the bench is ridiculous with this roster given he's arguably our best and most versatile perimeter defender, we are by far the worst defensive team in large part because of the IT/MT backcourt, and our backcourt gets abused on that end, whereas the SA's and OKC's, are once again, part of the best defensive units in the league.
There's another issue as well, in that those teams have a clear hierarchy. It's Parker/Duncan or Westbrook/Durant, and everyone else around them are defensive role players, and at least one can hit the corner 3. Bringing Harden/Manu off the bench is in part a strategy to not have those two step on the toes of the two main options. Both coaches have talked openly about this, in Pop and Brooks.
Us? We have a free for all every trip down the court where coach is yelling at everyone to just run and shoot, with no defined roles, impotent defense, and a coach who has no understanding of a proper sub pattern.