Just took a look. Harden was 22 (!) years old his last and most productive year in OKC. He was still a kid. And the offense was not centered around him, as it was more about Russ and KD. Still, his numbers were comparable (3p%, PPG, TRB/G, AST/G, St/G Minutes/per game), to Manu's first year with comparable minutes (about 30 mpg), 04-05, when Manu started every game (more attention, more plays run for him, Pop designing plays for him and letting him have the ball at the top of the key to go to his left every drive). And, Manu was fully in his prime that year, at 27. So your numbers argument is baseless.
https://www.basketball-reference.com...hardeja01.html
https://www.basketball-reference.com...ginobma01.html
And then you can look at today, when Harden is literally the face of his franchise for several years, each time leading them to the WC finals by himself, with CP0 out with injury, and still almost beating the all star Worriers. You really can't even compare the two, apples to apples. One is clearly far superior player, even if the other is a beloved Spur and a 1st ballot HOF.