I guess some of what you’re saying is true. But you’re not bringing up that, at least historically, one can sell a
DVC contract prior to expiration and probably either get your money back or see it appreciate in value…which means (aside from opportunity cost) that years and years of vacations can be covered by the maintenance fees exclusively. So, it’s an incorrect statement to say that money paid upfront is “just sunk.”
For me, the bigger plus to DVC, in addition to being on property (which of course is huge), is also the theming and design of the hotels themselves. I think they exist on an entirely different level than other timeshares, which might indeed have first rate facilities, but also a generic design you can find anywhere. For me, they don’t provide the immersive escape provided by DVC.