When looking at a rebuild, there's always the temptation to sign someone who's been in the league for a few years and seems like they still have potential. In the case of Zion Williamson, that is a dead end that would make the Sacramento Kings even worse off than they are at the moment.
It has been widely reported that the Kings are probably going to undertake a massive rebuilding process in the near future. When that happens and what form it takes remains to be seen, particularly since they have salary cap issues holding them back for this season and next.