KOA is largely very unfairly bashed for a reason that cannot be applied to most other parks. KOA's are a national chain but independently owned and operated. What other nationwide RV park has this kind of national exposure and recognition? Not many such RV chains. So when you find one or two KOA's that are lousy people tend to link them all as one. There simply isn't any other chain with so many RV parks tied together with a common name to make such a link. I have stayed at several RV parks that were lousy but a comment here would only apply to that one single park. But with KOA, a bad comment is linked to all KOA's because of name recognition.
That said I have stayed at horrible KOA's (Lost Hills, CA) and good KOA's (San Diego,CA or Williams, AZ). I do not link them. They're all independent as most RV parks are.