Okafor has potential, sure, but he's barely starter material until he develops further. Cousins is up there with Davis, KAT, Aldridge among the top 5 big men in the game.
Among centers, he's maybe top-25? Some guys who are definitely better options at center right now:
Cousins, KAT, Anthony Davis, Drummond, Whiteside, Noel, Horford, Gobert, P Gasol, M Gasol, D Jordan, D Favors, D Howard. Probably most of Vucevic, Dieng, Jokic, Monroe, Kanter, B Lopez, R Lopez. Porzingis or D Green, if you count them. Capela, S Adams maybe? Embiid if he comes back? Myles Turner?
Other young guys may emerge and pass him.
You pay a high price for Okafor and he would have some future potential, but he'll be a below average starter out of the gate and cost you wins. His absolute ceiling might be lower than what Cousins is right now.
Nobody was willing to part with a top-5 pick for Okafor. Every team outside of *maybe* Philly at #1 would have traded their pick (and more) for Cousins. There are no asterisks about salary necessary.
Would I trade a middle 1st rounder for him, or part with some guys from our bench? Sure. But I would be absolutely shocked if he fetched Smart, Brown, or any BRK pick.