I think that 10 years ago you had numerous awful QBs starting in the NFL, and then all those bad QBs were replaced in short order. So you have a lot of better, younger QBs all getting a chance to play right away. I'm looking at who some of the leading passers were in 2003, and you have guys like Kitna, Aaron Brooks, Tommy Maddox, Quincy Carter, Delhomme, Joey Harrington, Leftwich, Jeff Blake, Jake Plummer, Patrick Ramsey, Jay Fiedler, Kelly Holcomb, Tim Couch, Doug Johnson, Kordell Stewart (Bears)....ALL those guys are terrible, and thats over half the league. I didn't even include guys like Kerry Collins and Vinny Testaverde.
Also, it seemed like the entire generation of young QBs of the early 2000's all ended up being bad. Harrington, Couch, Akilli Smith, etc....all those guys were supposed to be the next wave of great QBs but it never panned out.