Dalton is actually completing significantly more passes than Manning did in their sophomore seasons, and their interception rates are almost the same. The big difference is pocket presence.
Manning made some terrible decisions with the ball in 2005 that I remember being eerily similar to some of Dalton’s, but under pressure he did a better job keeping his eyes downfield and making the pass. Maybe his completion percentage suffered for it, but those incompletions did not hurt the team as badly as the sacks did.
Sure, this is something that is curable. The light did not turn on for Manning until the Super Bowl run of 2007, and 2008 was his first complete season in which he played like a future star.
The point being that the end of Manning’s fourth season was the beginning of his ascent. Likely Dalton will never play up to the level that Manning is at now, but writing him off at this point is awfully short sighted. If Dalton does not begin to show improvement in the pocket next season then, yes, sound the alarms.
But, for now, keep in mind the learning curve. Jay Gruden may have thrown him in the deep end of the pool this year responsibility-wise, but if he does not drown then it could all be worth it.