Andy Dalton's scouting report hints at why you haven't won with him.
NFL Events: Combine Player Profiles - Andrew Dalton
OVERVIEW
Dalton is four-year starter and proven winner, but he will have a difficult transition to the NFL. He is undersized and will not be able to take off and run at the next level. He is generally an accurate passer, however he will make some poor throws when his mechanics break down. Also, he plays in a very user friendly scheme where he throws to a lot of wide open receivers and it is unclear if he can fit the ball into tight windows. Dalton will need some time to learn a more complicated offense and he looks to be a mid-round pick.
STRENGTHS
Dalton is a well prepared player that scans the whole field and makes solid decisions. Has a quick release, a strong arm and is an accurate passer, especially on the run. Has great mobility in the pocket and shows very good instincts as a runner. Extremely productive collegiate career.
WEAKNESSES
On the shorter side and has a three-quarter delivery which will likely result in a lot of batted passes. Deeper throws will float at times when he does not set his feet. Played in a spread offense and will have to learn a pro style system. Does not always feel pressure in the pocket which nullifies his good mobility.
^
The bolded above succinctly explains why Cincinatti hasn't won. You play Andy Dalton. He is, as his scouting report delineates, an undersized pocket passer with inconsistent mechanics that floats his deep ball and has middling pocket presence.
You're blaming Marvin Lewis when it doesn't matter what coach Dalton has, Dalton will always suck on a consistent basis. Dalton is not the best QB Cincinatti has ever had. Palmer is better than Dalton. If Dalton is the best QB you have right now, that just means your team should draft a new QB. If Marvin is behind Dalton's continuing to play poorly at Cincy, he should indeed be fired, but I'm not so sure that's the case when there's Bengals fans like you defending Dalton and shifting blame. If Aaron Rodgers had AJ Green, he'd go deep in the playoffs every year. Dalton has no excuse. Draft another QB and keep drafting until you hit on a top 10 QB.