With JVG, D came first...it does not with Adelman.
It's a lot like when Flip Saunders replaced Larry Brown and everyone was expecting them to keep playing D at the same level plus improve offensively...and initialy they did just that, until the playoffs.
Players have to be forced to play D...it is not something they are naturally inclined to focus on first, and if the coach isn't that way, the players won't be either.
Even Pop has to refocus the Spurs on D a few times per year...Adelman has never done that, and I doubt he ever will.