To clarify "90%" (not that anybody cares):
An OC playcaller assesses what's happening & thinks of an immediate play and perhaps what the next several (chess game) plays he'd like to set up. The current play is primary of course, but the future-looking set-up plays are not trivial. There are times when a certain play is call to check coverage and defensive game planning too. Hopefully these are not wasted plays, but, to my information, every OC calls some of these.
I have closely listened to NDs several game announcers' comments on the play calls. The total times that they complain about a Rees playcall on fundamental-gameplan-error grounds are very small. This last game, those "philosophical" objections were confined to two Tyree calls running laterally (one of which might have been the RBs wrong read rather than play design,) and the two series where we did not pound the run as much as we should --- the announcers even there admitted that Rees needed to call SOME passes.
So, calling plays which are "theoretically" understandable is different from plays that turn out to actually be productive. Hopefully that's obvious, but just in case: This is true because there are two teams on the field. Both teams are composed of talented trained players. Both teams will make plays and make them about half/50% of the time --- for sure the defense has to be successful CLOSE to 50% of the time, or football would be no game (just a heavily armored track meet.)
It's still debatable of course, but having listened to football people both in game and out speak of Rees' playcalling, I, along with my own eyes, believe that he usually calls a play that is understandable from a football perspective. Some of those plays fail due to lousy execution; some fail due to really excellent defensive athlete execution; and some fail due to the DC calling something wherein his defense shifts late into just the worst pattern for the play called. In those latter problem situations, the offense needs the QB to have such a calm and superb grasp that he gets the team into some other play, or improvises. Stop and think for a moment how often you believe Drew does that, in contrast to say, Ian.
I honestly believe that most "fans" understand football so shallowly that they don't think about any of this. (But they should before making really strong statements about where the failures arise.)