This team is old, but that has little to do with the problem. There's no rhythm and bad coaching. I don't think it's actual "chemistry" but more of sorry plays not built or ran properly. Each player in the 9 man rotation has skills to make a better offense run perfect.
Rondo - slash and pass or fancy layup(occasional dunk)
Ray - Pick and pop, catch and shoot
Pierce - slash, draw the foul and hit the J
KG - baseline jumper, post up fadeaway
Perk - Camp out in the paint and wait for a pass from KG/ Rondo
House - Wait for a pick and hit a 3
Marquis - Post up a Guard, spin and hit an 8' J in the paint
Sheed - same as KG all day, Wait at the top of the circle for 3
What I have noticed is that the plays ran aren't in a flowing sequence. If KG is cold, and Sheed is clanking 3s, Doc follows up with 1 play for Ray, then Pierce takes over. The ball needs to move. Sheed was taking too many 3s, now he looks like a troubled rookie not knowing when to shoot. Eddie the same thing. They're both passing up the shot. MD comes in, makes a nice play, then disappears.
I really feel like the team needs one more player that can create his own shot - whether it be off the dribble or moving better w/o the ball. AI would be great with his own shot, but he needs too many attempts to make points. Nocioni is a great slasher and draws fouls. What realistic trade could make this team run better, move the ball and get a good shot...