Political crap aside, Kaep's biggest problem is that an offense needs to be tailored to his skill set.  Nobody wants to be concerned with customizing their offense for a backup QB.
He would be a good fit in Carolina or Seattle.  I'm not sure he fits anywhere else.

As far as Henne goes, the narrative on him a few years ago was that he could be good if surrounded with talent.  He was promptly handed a team with 8 or 9 rookie and second year players on offense.  The team is significantly better all around now, but after 3 years of clipboard holding, how could he be improved?

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