again not dissing Mitchell or the need for a good back-up point guard at all. Just a back up point guard is not the target with a top 10 pick.
I think you might be overvaluing the expected production of a player picked in that range.
I looked over ten years' worth of drafts (2008-2017, so players have all had at least 5 years to play). I looked at picks 8, 9, and 10, so 30 players total.
Remarkably, there were only a handful of complete busts. Only 4 of the 30 players played in fewer than 50% of the games they could potentially have played in: Zach Collins (who is still only 5 years in, and has been hurt), Jordan Hill, Jimmer Fredette, and the biggest bust in that list, Joe Alexander (only 67 games total).
However, across the entire list of players, the average player only played in about 65% of games they were eligible for. And the average player only started 60% of the games that they played (which comes out to about 40% of all games).
Even so, this was skewed by several players who have been basically full-time starters. 6 players (20%) have started in 80%+ of the games they have played in. Another 9 players (30%) have started in 50%-80% of the games they've played in. And 15 - half of the sample - has not started 50% of the games they played in. Those 15 players only started in an average of 22% of the games they played in.
This means fully half of the players picked in that range should be expected to be bench players who occasionally start.
And, just to get out of the numbers game and into the names, here is the list of players, with breakdowns based on percentage of games started:
80%+ games started
C.J. McCollum
Andre Drummond
Kemba Walker
Paul George
DeMar DeRozan
Brook Lopez
50%-80% games started
Dennis Smith Jr
Marquese Chriss
Noah Vonleh
Elfrid Payton
Kentavious Caldwell-Pope
Brandon Knight
Al-Farouq Aminu
Gordon Hayward
Brandon Jennings
<50% games started
Frank Ntilikina
Zach Collins
Jakob Poeltl
Thon Maker
Stanley Johnson
Frank Kaminsky
Justise Winslow
Nik Stauskas
Trey Burke
Terence Ross
Austin Rivers
Jimmer Fredette
Jordan Hill
Joe Alexander
D.J. Augustin
I think it's fair to say that outside of Gordon Hayward, there's not really any player outside the top 6 that really moves the needle any more than we hope that Davion Mitchell will. The rest of the guys the the 50-80 class are kinda just "guys", and in some cases (Chriss, Vonleh) near-busts.
I know everybody wants to nail every pick, but this is kind of what's available at 8-10. Don't knock Davion if he spends the beginning of his career (if not his whole career) largely coming off the bench behind a top-5 pick. It's completely par for the course at #9.