I know what you mean, our reclamation district posted the whole island "No Fishing,Parking Etc." a few years ago for just that reason. I have grown up here since 1967 and watched "some" people ruin it for the rest with there careless disregard for the property owners here. These same people are quick to complain that there is nowhere to fish and don't seem to realize they brought it on themselves.
Just a thought for you though , I have visited virtually every lake and reservoir in California and I don't believe we are in better or worse condition than elsewhere.
My reason for building this project is to educate and inform the public so ,hopefully, they go home with a new respect for this unique ecosystem. There are 1000 miles of waterway in the delta, a lot of it is not trashy. Come visit and I'll show you.