Highly salted colored water with minimal solids is not what I think of as soup. “Cream of XXX” I use as a base for other cooking though. I just cut down on the salt in any recipes I use the canned soup in.
Salt. You nailed it.
The excessive salt content in Campbell’s Soup makes it taste terrible.
I started making my own cream bases when a recipe called for it - I always keep home made bone stock on hand-