I think a few years after Giannis was drafted, there was a wave of "Let's take some really raw big guy with limited basketball experience" picks. That in part explains players like Maker and Chriss going so early when there was little to suggest they were lottery talents. Bender is kind of a different story, but also follows a wave of lanky European players with limited playing experience at the highest level failing to make it. The foreign players in this draft were TERRIBLE and really tanked things in the first round. Yabu, Papagiannis, Ante Zizic, etc. Zubac in the second round was very good.
Simmons is such a bizarre story, nobody could have seen what would happen with his career.
Brown, Ingram, Siakam and Sabonis have turned into excellent NBA players. Jamaal Murray probably has the best-case-scenario for his career, minus the injuries, given what he was coming out of college. Dejounte Murray I've always found a little overrated but was obviously a great pick. Hield is exactly what people expected to him to be; an elite shooter in a league that values that highly. Poeltl is a very good player. Brogdan is one of the best draft picks in recent NBA history. Malik Beasley (19), Caris LaVert (20), Zubac (32) and Georges Niang (50) all greatly outperformed their draft position.
Kind of interesting to note that this draft was filled with highly touted big men recruits from high school that never did anything in the NBA. Skal Labissiere (ranked #2 behind Simmons coming out of HS), Cheick Diallo (#6), Diamond Stone (#7), Henry Ellenson (#9) and Stephen Zimmerman (#10) all didn't do anything in the NBA. You could throw in Ivan Rabb (#5) who was in the draft the following year as well.