There are very few sure bets in the NBA Draft, especially for those picking outside of the lottery. The further you move toward the back end of the first round, the more it starts to seem like throwing darts.
This is what makes the scouting process so important. Teams want to evaluate as many prospects as they can in a limited window, while the agents for those players want to steer their clients toward teams that could be reasonable landing spots so that their time isn't wasted. Every team would like to get a look at guys like Karl-Anthony Towns or Jahlil Okafor, but only a select few teams drafting at the top will get the opportunity.