The Celtics will remain in limbo until moves to get some stars present themselves. This is the nature of the NBA. For the teams that don't have stars, it is a waiting game. Some teams try to speed it up, either by tanking year after year, or by going all-in for players who are not really stars, but those rarely work out.
Unfortunately, it is stars league, and until you have those guys on the roster, it is hard to build a team to do anything but hover.