Interesting debate !
First, you should check our Kemper's settings like pure cabinet... and adjust the gain to your tastes and your guitar's pickups.
I think some disappointement can come from "very well mixed an mastered" demos of some profiles, I heard that sometimes, even about quite expensive profiles packs.
There is no problem with that of course, because that's a good way to hear profiles in a mix situation, but you can be lost when you will test the profile alone at home, without the EQ, the reverbs and the great bass tone besides.
Personnally, I never add any EQ or reverb on demos to show the "raw" tone of the profiles because I think it's closer to what you really get at the end, even with 4 guitars and a bass.