Around 2000 (and fading into about 2004), the ACC had multiple powers beyond Duke and UNC. Not all years, but Maryland was really good for awhile, Wake had some nice teams, Tech had a few good seasons.
About up to 2009, while the ACC only had a few great teams (really Duke and UNC), almost all its programs were solid. It was still deep but not necessarily at the top. There was only one bad team at the most each year.
In the last 3 or 4 years, the ACC has started to get a number of really bad teams -- Wake Forest, Boston College, Virginia Tech (this year), Clemson (last year), Georgia Tech (one year) . Maryland (one year) 4 or 5 sub 100 KenPom teams -- that did not happen until recently.
BC is on the rise. Clemson too -- with a Pitt style. Maybe Tech will change it around with the coach from Dayton (Hewitt was a disaster). Syracuse, Louisville and Pitt is strengthening the top. Hopefully, teams like BC, Wake Forest and Georgia Tech will at least become respectable.