Ainge has said that he has no long-term plan and is just trying to acquire as many assets as he can, which is in fact a plan. His idea is to try and turn a bunch of players/picks into an attractive enough package to get a star, which is what the Celtics need. Stevens is an excellent coach, but he isn't going to win anything without talent.
Drafting CMac would be par for the course with Ainge. Like he did with Fab, he's going to try and swing for the fences with a later 1st rd pick. If he misses, it's not going to kill the team, but if he hits, he's closer to building a title team.