This is the case.
The ACC hasn’t been a top 3 conference since 2019.
Prior to 2019, the ACC was a top 3 conference 17 of the prior 20 years by the same metrics (namely KP, but whatever you want to use) we use today. So it’s not the metrics that have changed, it’s the quality of the ACC.
A big part of this is other major conferences getting bigger as PH noted. Another part is the SEC recently started to outbid the ACC for top tier coaches, and then started getting some of the top tier southeast talent that used to end up in the ACC.
We have been clearly behind the SEC in each of the 4 years since the season the tournament was cancelled. We were behind the SEC in just 5 of the 21 seasons that preceded that.
And then lastly, the bottom 5-6 teams in any given year have been awful. Not just not very good, but still beat the dregs of D1 (which was the historical standard for a bad ACC team), but lose at home to Citadel, Chattanooga, Arkansas St, Western Carolina, USF bad.