Over those 15 years, the AFC has won more superbowls (9-6) and has a better head to head inter-conference record, although most of that was from 2001-2009 when the AFC destroyed the NFC by almost 2:1 some seasons. Last 5 years have had an edge to the NFC but not enough to make up for the 10 years prior.
I agree with the narrative that the AFC has been dominated by 3 teams and then a lot of average teams below, but it's not like the NFC has been so!e stellar example of amazing high calibur football since 2001 either. A lot of garbage there too.