IMHO, if dining is such an important part of your criteria, I would not be rushing to Vegas. Not that there aren't some excellent dining facilities there (albeit on average a price often significantly higher than at WDW, IMO), but Vegas, too has a higher priority than dining. Vegas wants you to gamble, Disney wants you to spend $$ at their parks (and not just for admission). The majority of dining options in Vegas have also increased substantially in price while (noticeably) decreasing in quality. Of course, if you have not been a regular visitor to Vegas, odds are you will not be aware of the changes, just as is true for the "newbies" and future guests of WDW. I have noticed the same change in cruising, as well. We have been regular cruisers for many years now. The dining experience has deteriorated greatly, IMO, but people still book.
I think there is a recurring theme here: vacations such as Disney, cruising and even visits to Las Vegas were once geared to a wealthier clientele. In the quest to draw more visitors, the reality is the best way to up the bottom line is to increase the number of bodies entering one's domain. It's why the Atlantic City casinos subsidize so many bus trips - the avg guest arriving by bus may not be a high roller, but as a group they are loyal and steady patrons, and they affect the bottom line, not to mention "appearances" (who wants to play in a casino that appears empty all the time?); the casinos cannot afford to turn their noses up at such volume, either.
I'm sure Disney will miss you, and Disney is more likely to at least acknowledge your dissatisfaction than many companies. However, if in the long run the
DDP allows more patrons to return more often, they will allow you to leave. Just as Las Vegas is not in the "family vacation" business, Disney's primary business is not dining.
BTW, I do agree with you that the loss of quality in dining is sad (although you might use a stronger word

furious:?), but it is definitely part of a larger trend within the industry.