The Bengals are a mess, and much of that has to do with the defense.
While the offense certainly had its issues Sunday, the game was lost in the first half when the defense allowed the Saints to reel off 35 points, which is tied for the most allowed in one half in the Marvin Lewis era.
By the time the offense got the ball a third time in the first half, they had already scored once and drove deep into Saints territory another time before a false start forced a punt on 4th and 6, yet still trailed 21-7.