The blame is on the front 4. They generated very little pressure...thus giving Ryan even more time to pick apart an already depleted secondary.
There's lots of should've could've's...but to me, the lack of any pressure on the line was it. The huge percentage of 3rd and long's converted by Atlanta aren't the O's or ST's fault.
Granted, some better playcalling in the redzone would have helped drastically. Also, so would Harris not giving up on the play and tossing the fumble recovery away like a used napkin.