I loved AB as much as anyone else here did, and he may very well be a better player than Morris is. We don't know yet how Morris will play in our system or how AB will play in Detroit's. But if AB does fare better, maybe Detroit got the better end of the deal in the short term. However, can the Pistons convince AB to stay? And will they be willing to pay him what the market dictates next summer?
Same two questions would've applied to the Celtics if they'd kept AB. I think the C's could've convinced AB to stay, but probably wouldn't have been willing/able to pay him what the market will dictate. If Detroit ends up being unwilling/unable to retain AB next summer, then this may turn out to be a bad deal for the Pistons for what amounts to a one-year rental of AB.
Also, as others have said, this move didn't occur in a vacuum, as it was necessary to create the money and/or playing time needed to sign Hayward.
We'll see how this trade looks two or three years down the road, but as of now, I'd consider it a pretty even deal.