We close all RV windows, doors, and vents while maintaining air pressure within the coach using a roof vent fan ... except for the vent with the fan in it. Very little air gets out except through cracks and leaks, hence very little hot air comes in. The result is a slight pressure being maintained within the coach - just enough so generator fumes cannot enter through any cracks and leaks in the coach's structure down low where the generator is. We also do this when traveling on unpaved roads to keep dust out of the interior. The technique works like a champ in both situations.
One cannot compare use of A/C all night when drycamping to use of A/C all night in a hookup campground. They're not the same type of RV camping. Using the A/C all night powered by a generator is because for a specific reason you intentionally do not want to camp at, or can't get to, a hookup campground. As expensive as self-contained RV's are, owners should be able to camp anywhere anytime in relative comfort for short periods of time - unless the builders of some of those "self-contained" RVs did not do a good enough job designing and/or building of those self-contained RVs.