Not trying to be a troll on your post, but do you even watch the NBA? Cal basically has supplied half the young talent.
Karl-Antony Towns, Anthony Davis and Demarcus Cousins are arguably the three best young bigs in the game. They have other players succeeding to like John Wall, Brandon Knight, Devin Booker, Eric Bledsoe and Julius Randle. The one and done has worked well for them.
Personally, I agree I wish they stayed longer like CFB. I wish we saw more of the Buddy Hield's of the world, but it is what it is. While the one and done rule isn't helping college basketball at all, it definitely hasn't hurt Cal and his supply of NBA talent.