2015 Dodge 3/4 Ton Really Not Camper Compatible?

Upgrades can be made to carry more weight. TC owners and others do it all the time. It won't change the official rating on the sticker. Some up-fitters can do that but likely won't on a 2500.
The diesel is heavy, most 2500 trucks with diesel engine, 4wd, crew cab, lots of options, etc. just don't have much payload.
I'm actually glad to hear of a camper dealer concerned about weight capacity. Most of the ones I've heard about or talked to would sell their biggest model to a guy with a 1500.