The problem? No.
I do believe he has put up a lot of unimpactful numbers in his career thus far, but I don't think he's a cancer or anything.
I think there is a lot of talk on this forum right now about him being what fans want him to be and believe he can be, but that doesn't mean he's shown it thus far. To this point, he's never shown the ability to make a large difference in winning basketball games. *should* he be able to be a defensive anchor? Yes.
He's got the physical talent and size, but his motor has often been an issue, and I don't think he plays anywhere near to within his limitations.
All of that said, he's made multiple all-star games for reasons, and he is capable of leaving his large footprint on games. I believe he could be one of the better players on a really good team if he plays focused and within himself.