In general I agree with the OP that I'm sick of the Celtics getting out-rebounded most games. And I'm sick of the Celtics committing too many turnovers by their starters.
But part of the rebounding number discrepancy is a result of the Celtics mantra of getting back on defense to prevent easy fast break points. This results in a lack of offensive rebounding, which we have to acknowledge is a result of the team defensive concept.
However, when this team doesn't get enough defensive rebounds it really frustrates me. Defensive rebounds are a result of technique in boxing out and desire to get the rebound w/o worrying about running down the court for a fast break.
Side note - KG at center seems to work for him because of his rebounding technique. KG, in my opinion, has never been great at boxing out. However, he is very good at timing a jump for a rebound (plus his long arms, etc). For this reason, when he is at Center and near the hoop he can take advantage of his timing and it minimizes his inability to box out.