And another difference is that KD does not actually suck on D, he is above average. And he grades as way above average in foul rate, isolation and pick&roll D. He's above average in PPP and Stl%. As a shot-blocker (Blk%) he's ranked 41st, 23rd, 30th, and 20th the past 4 yrs, and most of the guys above him are 15 to 20min a game back-up center D focused guys.
His % was tied for 20th 5 yrs ago, but didn't play enough to qualify. He is a very good to elite shot blocker, you can expect him to be top 30 in the league in Blk%. And he's done this as an O-focus, high usage, elite O player, which makes his D even more impressive.
His D has been much better since moving to the Big W/4 position and he does it without fouling much. He has learned to positioned himself correctly and use his length, he is not a below average defender. That is simply not true.