Just be aware that DVC makes up about 15% of all on-site rooms. Considering that a large percentage of theme park attendance comes from offsite hotels, DVC members make up a very small percentage of overall theme park attendance.
This percentage hasn't fluctuated much since the opening of Old Key West in 1991 because even as Disney added DVC rooms, Disney also added much larger Value Resorts. (Recent conversions at the Poly and WL involved a relatively small number of rooms, while the VGF is tiny by WDW standards.) Going forward, this ratio will change with what's going on at CBR and CSR.
Instead, what's driving crowds during the off-season, including early December, are changes corporate Disney has made to how it prices and markets WDW. The International Festival of the Holidays, Mickey's Very Merry Christmas Party, Pop Warner, Run Disney, Food and Wine Festival, Flower and Garden Festival, Florida resident discounts, and the new Festival of the Arts are all designed to attract Guests during (the no longer) slow season.
The first week of December is crowded because of how Disney markets and prices that week.