Fair enough, but Karl Malone wasn't exactly a defensive juggernaut. A good defender in his era of basketball. I wouldn't go so far as saying he was a great defender as you suggest. I will say this about Karl Malone's defense, he wasn't afraid to foul hard. I think that in itself helped him defensively, at least from a psychological perspective. Players would be very wary of his elbows when attacking Karl Malone.
But, defense and rebounding isn't why Karl Malone was considered the greatest power forward before Duncan got deeper into his career. It was his scoring. I'm just suggesting how his offensive ability was aided in a similar way that Amare's has been yet also criticized. It's true Amare gets criticized much more for his defense and lack of consistent rebounding, but he also gets bashed for what is perceived as not having a back-to-the-basket low post game.
I do think Karl Malone's legend is greatly tied into his durability and longevity.
Again, allow for Karl Malone's career to overlap more alongside the late 1990s to currently, while other great power forwards like Duncan, KG, Dirk, Gasol, C-Webb, and Bosh had the prime of their careers, and I don't think he'd be mentioned as one of the greatest players of all time, but for the longevity of his career and his ability to put up very good stats deep into his career. But then again, I don't think he'd have two NBA Finals appearances or either league MVP.