No way Aminu can ever touch Marion offensively. Marion had way more in his arsenal coming out of college, even if it wasn't pretty all the time. People need to quit being delusional on here.
While Aminu's turnover % has actually gone up this year slightly (from 18% to 21%) his assist % has nearly doubled (7.2% to 13.5%). His Asst/TO ratio last year was 0.714 while this year it's up to 0.926. He's getting there.
Also he's taking 3 pointers at a lower rate than ever in his career, and while I don't have any data on mid range jumpers, it appears he is taking less of those as well. He's realizing what he's good at and what he is bad at and he is starting to become great in a few areas (finishing at the rim, rebounding, making plays on defense) which is what makes you starter material. If he could ever neutralize even one of his weaknesses (ball handling, shooting, decision making) then I think he could be a starter on a championship team if the other pieces around him are right.
I see no reason why he can't be a more athletic and bigger version of Tony Allen down the line.