It's simpler then everyone is making it seem.
With Ben the Pistons failed to win another championship in two consecutive years.
He was the most important part of their defense, which was the most important facet of their game.
They lost Big Ben, did not find an equivalent replacement, so they downgraded as a team. They downgraded from contending for, but failing to win, championships. Ergo, they no longer have much of a shot at rings.