I don't think it is that others are more prepared but disney is a larger place with more moving Parts then either of those. The majority of questions people have wouldn't apply to either of those. As an example, six flags says we are doing reservations based on membership level. Done. With disney you get questions like "what if I have an AP and have booked a resort but haven't bought tickets. Do I get a reservation?" Or "is a reservation good for one park or can I hop" or "what if I have reservation at one park and ADR at another" or "What if I had a FP that is now outside of new park hours" or simply "what is resort transportation (or transportation from TTC to MK) going to look like" etc etc.
Disney is more complicated due to FPs, multiple resorts, DVC, ADRs and all of that which six flags or universal don't have to deal with.