None of the majors seem to work that well in NW Kansas/NE, especially off I-70. (I can't speak to I-80 past Omaha as I don't ever get that far north of the Ks border or into the panhandle.)
Verizon does better than most. I've had conference calls by cell where they couldn't hear me but I could the others, and low bar Internet or cell based that was very weak or spotty outside of larger towns like Hays, Colby and Holdredge.
I finally have gone to a satelite phone when in the off beaten path areas you note, Enchanting, and that seems to be okay, though it also uses the majors. My experience has been like yours out there. A lot of that area is served by Nextech/Rural Telephone which is a Sprint knock off co-op that I think is now on their own, so the majors have somewhat surrendered the flyover space to local independents. It also seems stronger in former SW Bell territories.