I'll just say this about stars coming to Boston via free-agency, when where we actually in a position (having cap space) to acquire a star free-agent and we missed on it?
So I don't see it as much as no stars coming to Boston, but when has Boston actually been in a position to acquire such a player in the first place? I would bet not many.
I'm fairly certain the Celtics have never once had the requisite cap space to sign a "max" FA. At least not in the modern CBA-era. Hard to sign a player the rules prevent you from signing.
I suspect that if the Celtics were to find themselves with the cap space to do so, and still had Rondo and Sully on the roster, it's quite possible a star would want to come here.
People need to understand, the Celtics are the 4th most valuable NBA franchise, as valued by Forbes. They're not LA, Miami or NY/BKN. but they are a highly respected franchise and the most successful. Not everyone can play in the glamour cities, even those teams have to abide the salary cap rules.