There are options to paying your dues up front - you can have your dues drawn out of your checking account monthly making them more manageable.
In my mind, I think the drop in satisfaction could be tied to a number of issues. I for one don't like the fact that every time you turn around you see a discount for a WDW vacation and none of it ever applies to DVC members. I know we supposedly have "perks", but many of those are stagnant and don't change that often. Like the AP discount - it's been $100 for ages but year after year the cost of these go up thus eroding the value of the perk.
Not getting "free" dining may sour some people's attitudes as well. There are a laundry list of issues I could throw out there such as resort availability in your window, ever increasing points required for other venues such as
DCL, CC, etc., blackout dates for pool hopping, general room cleanliness issues, you name it....
This survey is a snapshot in time. If the trend continues to go down or stay stagnant, then I think DVC should take a hard look at the "why" of the matter and try to correct it.