I think the only real chance the C's have of not being bad for the next 4-5 years is unfortunately if they can move Pierce in such a way that they free up that cap space. By my guess, he's already moved quite a bit in that direction in the last couple of weeks by leaking the possibility in the press to show Wyc that the TD Garden wouldn't burst into flames at the mere suggestion of it and thus getting ownership's blessing while starting discussions.
I don't think it is the Boston weather or history or Doc, Danny or the ownership that has kept DH and the other big fish from wanting to land in the relatively small, cold Boston pond.
IMO it is 2 or 3 factors:
1) that the Fossilized Three are still here, guaranteeing that Boston is a declining team and still 'somebody else's' team,
2) that there hasn't been a clear path to immediately getting three in-their-prime All-Stars onto it, and
3) maybe also that Rondo is just a little too weird a guy and not to the social taste of DH and his like. (Though as others have noted Josh Smith could be the glue here.)
If Danny can clear out #1 and somehow create a path to #2, possibly via swapping out #3 I think the whole game changes.
And, the right sort of dumping (sorry) of Pierce's contract could make that happen, since it could open up the cap space for two max deals. Yes, it's still a long shot, but getting the C's into that position is a favorable enough situation anyway that it only makes sense for Danny to try to do it.