Once it's established that you have a Championship contender, you have to add the pieces to continue and reinforce it. Rookies/Sophomores are bench players on playoff teams.
For reference, the best the Warriors could do drafting in the backend since 2013 is Kevon Looney in 2015 and Jordan Poole in 2019, they're part of the rotation after multiple seasons of being non-factors. They drafted 2 players in the lottery in Kuminga and Moody and they're lower on the depth chart than guys like Juan Toscano-Anderson, Damion Lee, and Otto Porter; Wiseman got less minutes than Kevon Looney in a tanking year!