Respected area hoops coach Brian McCormick blames the coaching and personnel transition for the Kings' struggles:
With Mussleman (sic), the Kings still run some of the old motion; the occasional post split for a Bibby three-pointer or a Martin backdoor. However, Mussleman is more of a traditional, defensive-minded, pick-and-roll or set play coach. But, his personnel is not built for his system. He has offensive personnel trying to become a defensive team. It's no surprise that Williamson is again one of the Kings more effective players, as he fits a more traditional style of play better than Thomas, Miller or Abdur-Rahim because of his low block post moves and toughness on defense.
I think McCormick is right in large part concerning the problems with running out a set play team with Princeton-style players like Mike Bibby and Brad Miller. The good news is that Shareef Abdur-Rahim, Kevin Martin, and John Salmons are better fits for the Musselman system, and those are the guys who are likely to be on the roster for the long-term as Bibby and Miller will assumedly move on.
There's also a nice defense of Rick Adelman w/r/t the Mike D'Antoni era in there, so read the whole thing.