OKC has had 8 1st round picks, including 3 lotto picks, over the last 7 years if we assume they shadow drafted Sabonis. They have 2 good rotation players, one maybe, and 5 non-NBA players to show for it. Also, none of their 2nds have hit during that span. That's not the worst draft record in the league, but it's also not good.
So that puts the 3 lotto picks as Adams, Sabonis and Payne right. That's 2/3 success
Other picks (looked it up)
Archie Goodwin: Traded Draft night for Andre Roberson. All NBA Defense 2nd team Success
Alex Abrines: Above league average shooter (rare for OKC) good ball handler, improving defender. Currently out of the league due to illness/personal reasons. At pick 32 that has to be considered a success. Current issues not withstanding.
Mitch Mcgary. Draft success, developmental failure
Josh Huestis: Couldn't shoot but was a good defender, it's mindblowing that he didn't get more minutes given how short they were at SF. He was actually reasonably productive his final year in OKC when Melo demanded that he play. Was signed by San Antonio this offseason despite having a broken foot. So clearly they see something as well. Grading Failure. TBD talent, definitely development.
Cam Payne: Stunted development, had but hasn't shown much elsewhere. Failure.
Sabonis. 27th in the NBA in BPM this season. Success.
Ferguson: Productive NBA player. Still young but showing flashes. Only developed because another starter got hurt. Grade too early, moderate success.
That makes them 6/8 on those picks by my count via draft and 3/8 after talent development. The draft rate is actually pretty good. Talent development was ass. As is their training staff.
Edit: also Abrines was a 2nd round hit but generally OKC didn't either have the roster space or motivation to develop those guys.
When your teams the past few years are
Westbrook Augustin Waiters Roberson Durant Ibaka Kanter Adams
Westbrook Semaj Oladipo Abrines Roberson McDermott Grant Sabonis Kanter Adams (All developed except Semaj who was a bad G league player)
Westbrook Roberson George Melo Adams Felton Abrines Huestis/Ferguson Grant Patterson
Melo was bad and they had no bigs (Which is why they lost to Utah) that team was better then their record
Westbrook Ferguson George Grant Adams
Bench Schroeder + Shit
OKC lost a lot of wing depth and their coach chose not to develop it. They are Currently playing Raymond Felton at SF these playoffs.