If New York and LA are "ahead of us on the rebuild" then they are ahead of us because of reasons nobody can control: free agents will always want to go to those cities even when the franchises have been mismanaged and driven to the ground.
In that case we should just stop worrying about it. No matter what we do, they will always be "ahead of us on the rebuild" regardless of what assets we have and that's just something we can't change. There's no point in fretting about it.
Well, apart from their attractiveness to free agents, the Lakers have the #2 pick in this year's draft, and the Knicks have Melo, plus the #4 pick.
Those are major pieces the likes of which the Celts haven't been able to procure so far in their rebuild. They picked 6th in last year's draft, but it looks like they came away with a nice defensive role player / starter, not a stud.