2 main things (again, not his fault, it's just who he is & he's doing what he normally does):
1. He's typically in/around the paint. LMA really isn't stretching out to 3PT line too often so their men are typically more bunched up than normal. Dedmon likes to finish lobs/around the rim and also likes offensive rebounds so he's handing around the paint.
2. Even when Dedmon is further out (like setting the screen) since he has no real threat to score from there or put the ball on the ground, his guys sag off of him pretty much. He's great at rolling to the rim and sucking his man in that way but most of the time with him and TP in there, their men don't have to really respect them.
It leads to spacing issues for LMA and in general and is part of the problem (besides missing good looks) why things look out of sorts on offense with the starters.
They are still getting decent enough looks, but there is a reason why with Pau and Lee the offense looks better