I don't get the debate about Atlanta. Their top 3 and possibly even top 4 played better last than anyone on the Celtics is going to play this year in all likelihood. Starting with Horford and Milsap, they are good, there is no way we are going to get that kind of play out of say Amir Johnson and Sullinger. Sullinger may be able to play as well as Milsap did last season some day but I don't see it next season.
As for Teague, he had a great year last year. Smart may never be that good (he may also be better someday) much less this season and Thomas can't be what Teague was last year either. Thomas is great off the bench, very productive, but not steer a team to 60 wins kind of play.
As for the fourth (Carroll), he may well have benefited from being on such a balanced team but I am not sure we have anyone who can score as he did.
Atlanta had a special year, a couple players "broke out" all at the same time which in theory could happen to Boston I guess (Teague, Carroll and Korver I consider broke out, Horford and Milsap are just that good). More realistically, even Atlanta might not win 52 games, and the Celtics are a poor man's Hawks at best (barring multiple breakout surprise seasons).