I'd like people to do a little exercise: Imagine that the Celtics have the Kings' roster. What sort of return would you want to not be displeased with Ainge trading Demarcus Cousins away?
I'd be displeased with the situation regardless, unless I guess the return was Lebron, Durant, Curry, or Anthony Davis.
But if he had to get traded, I'd only be satisfied with a top 5 pick (in a good draft), a prospect with high upside or an established young player, and additional future draft assets.
Example: 2015 Top 5 pick, Vucevic, and a future first round pick.
As for this notion that Shaq or Hakeem would score 40 per game in today's league, I think the opposite is true, actually. It's tougher than ever for centers to score a large percentage of their teams points because of the emphasis on perimeter play and spread pick and roll offense.
You don't see teams having their center set up shop on the block and get 20 or 30 post up opportunities a game.