I suggest this trade assuming Okoro is the starting small forward and McBuckets is his backup. When the defense puts in a slower wing, Doug matches up with that guy as the small forward version of KLove.
Before this trade -- maybe?
Now, I think this would be a terrible trade. McDermott is an unplayably bad defender.
RAPTOR has him as the worst defender (over 1000 minutes) in the league last year -- and it wasn't even close. -4.5 Defensive RAPTOR, and the next closest player is -3.8 (and there are only 5 players worse than -3).
And it's not an anomaly either - last 4 seasons, he's never been better than -2. Only Colin Sexton and Trae Young have managed to post a worse defensive score over those 4 seasons. But the difference is that McDermott (except for last year) has been doing this primarily as a backup who has not had to go against elite offensive talent.
D-LEBRON likes him a little more -- (but still the 4th worst defensive SF last year -- though they confusingly mark him as a PF).
The problem with him being the "SF version of Kevin Love" is that he is much much worse than Kevin Love -- probably better just to put Love out there at SF -- he'll get toasted just as bad, but will at least give you some rebounding.
To Add: "Before this trade" this made a little more sense, because our offense could get really really bad when the ball wasn't moving, and McDermott could at least work with Garland to give you a reasonable shot.
Now we have two players who have reasonably high efficiency on ISOs off the dribble -- our offensive "floor" per position has increased dramatically now that DM will be taking the last minute 1 on 5 circus shots instead of Caris Lavert... I think that decreases the need for a completely one-dimensional offensive player like McDermott, and means that our 3&D target should lean more towards D than it has in the past.