Remember, part of it is a marketing tool to encourage people to buy direct. If you read the contracts, benefits that come with the "blue card" are not guaranteed for anyone, which is why they have been able to put in the restrictions on the points.
In terms of dues, those would not change, because it is based on the number of points at the resort. Once those have been declared, they can't add or take away points, so having the resale restrictions and a different set of owners will play no role in this.
Disney wants people to want to own forever and yes, it is not necessarily realistic, resale value is not there concern. The good news is that people who buy resale do save a substantial amount of money and much of that can offset the savings you get from owning direct points or grandfathered resale points.
Of course, if one really wants them, Disney does allow you to buy 100 qualified points.
Timeshares are timeshares and in comparison to most, I still think even with restrictions, people buying a
DVC resort resale, gets a good value for the product.