While the Sacramento Kings need a lot of work, the main area of concern is defense. That's why they brought Precious Achiuwa in, a noted and respected defender. And he has definitely boosted the Kings' defensive presence, though it's not a problem he can solve completely by himself.
The Kings' issues on defense have been going on for a long time. For several seasons, there was a focus on building a team that was driven primarily by offense. Without a reliable defense or consistent playmaking, it was impossible for that offense to take any kind of shape.