Competitiveness in divisions change. 10-15 years ago it was Cam, Brees, and Ryan in the NFCS. I can remember when the NFC West was laughable. It changes.
Divisions matter. If you want to go to the playoffs, win your division, you play 90% of the same opponents.
If you get rid of the division winners mattering then just break up the divisions and let the whole conference play each other.