It got to the point where it hurt to watch. But the simple fact is, even without the rebounding, they could have won the game. All they needed to do was execute consistently when they had the ball.
AI was fine, it was everyone else on the team that wasn't working hard on the offensive end. This team is capable of putting up 120 points on almost every team in the league. Most of the other teams cannot score that many points consistently.
There's a simple truth to basketball, which is that everytime you score, your opponent gets the ball. Once your ahead, all you have to do is score every time down and you win. So I'm less concerned about rebounding and defence than I am with offensive consistency.
When the Sixers are sharing the ball, running plays and working hard to get good looks, there are few teams that can stay with them. Most of the time when they loose, it's because the other team takes them out of their game. I think that what really happens is that the Sixers regress into a "me" team, too many players trying to do it one their own, rather than being successful as a group. It's very easy for this to happen, since AI is happy to take every shot in a game if he can. IMO, Cheeks has to force the team to run plays when that happens, just demand that they run the same plays over and over again until the other team stops them.
If Cheecks can impose that discipline on them, they will be fine, even with their limitations. But the margin for error will be small as long as they can't rebound or defend.