I'm tired of them, but I wouldn't say it's bad for the league. However, it IS an indictment against the rest of the AFC, especially the East and South.
Pittsburgh is the only other franchise that's been competently run since 2000 (you can make a case for Baltimore too).
Baltimore has had maybe 4 seasons of good quarterback play in franchise history (not even great or consistent, just good/decent) and haven’t had a competent coaching staff since 2007. Whenever they get on a roll, they immediately stop doing what was working to do the exact opposite, even going so far as to go prevent defense up 3-7 points with 2 minutes left in the game. To be honest, they’ve drafted badly most of the last 12 years too. They’ve spent two picks higher than a 4th rounder on a receiver since 2006 and spent seemingly a decade not spending higher than a 4th or 5th round pick on a corner except for jimmy smith. It’s really just Pittsburgh and New England.
Edit: For some added perspective, the jets, bills, dolphins, bengals, browns, raiders, titans, and jaguars have won a combined 9 playoff games and reached a combined 3 conference title games since 2003. That’s half the conference that has basically been bad nonstop. The only consecutive playoff seasons in this span by any of these teams is the jets in 2009 and 2010 and titans in 2007 and 2008, and the titans lost their first playoff game each year. By comparison New England and Pittsburgh have won a combined 30 afc vs afc playoff games since 2003. That does not include their 6 super bowl wins since then.