First, serious rain events that adversely effects the grounds only occur about every ten years. It’s highly unlikely any significant investment to mitigate the issues would made.
If the grounds can’t support vehicular traffic then EAA should have a plan with WiDOT to have more and better signage in place along the 41 corridor. Starting at 30-40 miles or more to the south for sure. This should include status of parking for daily parking. If Camp Scholler grounds are compromised then they could wave off the RVs and prevent the stack up onto 41. Getting to Fond du Lac and discovering the grounds are closed is too late due to the limited number of exits.
I do think EAA works hard to make the best of a bad situation for all. They sometimes don’t do a good job sharing their reasoning and the optics of looking in from the outside in can be poor.