So far, Bennett is the biggest bust ever. I get that he wasn't a consensus #1 pick, but [regardless] he was the #1 pick and he has been a total failure so far.
But, I don't think all is lost. While he probably shouldn't have gone #1, he was never going to slide past #8 or 9 because of the ceiling other teams saw in him. He may not be the next big thing, but high lottery selections are often give several chances to turn it around and it is entirely possible he finds a situation that works for him.
Turner is a nice example of what to expect from a player who didn't initially meet expectations, but found a situation in which he was comfortable. He doesn't need to be a star, he just needs to find a home.