I don't see how you can characterize that as 'terribly inefficient'.
....
So, which Jeff Green are you talking about? The healthy one or the obviously injured one?
Note I said he's "not terribly efficient" not that he's "terribly inefficient." Jeff's a lukewarm cup of tea; not really on one extreme or another.
That's really the point I've always made with Green, by the way -- though it's far from a novel opinion: when Jeff isn't scoring in bunches, either because he's got a favorable speed / size matchup or because he's hot from outside, he doesn't bring much to the table.
The inconsistency of scoring is to be expected because Jeff is just not THAT talented / skilled a scorer, and while he's got great athleticism and uncommon speed for his size, he doesn't often physically overpower opponents, unless there's a really glaring mismatch. I'm not sure that Jeff always brings consistent effort and / or focus, though, particularly on defense, and that troubles me much more.
As for your argument about healthy Green vs unhealthy Green, that seems to be one you're fond of making. Last year it was recovering-from-surgery-Green vs healthy Green. This year he's got a shoulder injury, I guess. Injuries are part of the game, and if Jeff spends substantial portions of each season playing at a lower level, then that's fair to take into account as a weakness of his.