The reason the NBA has such a high failure rate for draft picks that, unlike hockey or baseball, are expected to be "ready to play", is that the players are so young when the NBA drafts them. If you go back to the 90's or 80's, the drafts were pretty accurate representations of how the players would ultimately turn out. And when a team "whiffed" on a lottery pick, the pick was still usually a serviceable NBA player, not someone that was unplayable.
The 2013 draft may be the worst draft in NBA history. Despite a complete lack of talent in the draft, the best player, Giannis, went 15, Rudy Gobert was 27, CJ McCollum was 10, and Dennis Schroder was 17. Oladipo was the only player in the top 9 who became an above average NBA starter. If the NBA GMs were so smart, those 5 would have been 1 through 5 in a draft where everyone else basically sucked.
Even a good draft, like the 2018 draft, still has huge mistakes, such as Jalen Brunson slipping to the second round, when the second half of the first round was mostly role players, deep bench players, or players already out of the NBA. Brunson's sin was being too old on draft day. IT is worth noting that two of the best players in the back half of the first round in 2018 were older players, Huerter and Allen.
And when a younger draft pick, like Anfernee Simons or Lonnie Walker, does develop, it is years later, after the team drafting them has spent millions on a player they couldn't put on the court, and often the team that drafted the young player that eventually developed has nothing to show for it.
I am not the only one that feels this way. Many teams dump draft picks like they are Bed Bath and Beyond coupons. If you are an NBA GM, you are better off trying to build a supporting cast by drafting older players and through free agency, and then hope you can land the big star through free agency or a trade. Trade your picks for players that can actually play. Or you can keep wasting high picks on the talent equivalent of powerball tickets (with a similar % chance of success) and keep the Detroit Pistons company at the bottom of the NBA.