That’s an interesting statement and bears more scrutiny. Exactly how often can you find a Giannis at #15?
Well, oddly enough it’s happened twice very recently, with Giannis and Kawhi Leonard, who was also taken at 15.
But those two guys are two of the best picks in NBA history. The only pick I would put above Giannis and Kawhi is Kobe Bryant. Kobe was taken at 13 and ended up being a top 10 player in NBA history.
My point being, the chances of getting a player of Giannis’s stature in the middle of the draft happens about once every 25 years.
If we expand the conversation to all-star caliber players taken from pick 10 to pick 20, however, there are plenty of examples, and almost always at least 1 in any given draft.
Examples (I won't use 2019 because it's far too early to tell there):
2018: Porter Jr (14), SGA (11)
2017: Donovan Mitchell (13), Bam Adebayo(14)
2016: Sabonis (11), Caris Levert (20)
2015: Devin Booker (13)
2014: Levine (13), Nurkic (16)
2013: Adams (12) Giannis (15)
2012: Fournier (20)
2011: Klay (11), Kawhi (15), Tobias Harris (19)
2010: Paul George (10), Eric Bledsoe (18)
Now, not everyone on this list has made multiple all-star games and there are even a couple not to make one but have the talent and are considered fringe all-stars. The point is that while it's rare to find a generational talent this late in the draft, there are plenty of guys who go on to have the careers we expect out of someone taken top 5.
The good teams find and develop these guys. Obviously there's a little luck involved, but the talent is always out there to be spotted.