FWIW, it may be "harder and harder" to Exchange weeks ... but the same is true of Points systems, also.
Developers are building to de-value Points Systems so that what you buy and own today is less effective in years to come. Points systems might "flood" the market with expensive, high-end unit types that generate huge quantities of points for them to sell ... while the average owner will not hold sufficient points to book such a large, deluxe unit; creating more competition at legacy locations and unit types w/in the system. Point systems might also change the rules regarding reservations, again making it more difficult for the average owner while claiming they did owners a benefit by restricting the "evil owner who rents their timeshare excessively." At least with a Fixed Week, especially if you like the resort you've purchased, you can always go back and use that resort week.
Basically, both sides get "harder and harder" for the average owner as the developer works harder to skew the game in their favor, increasing direct sales and side-game revenue (rentals from the developer).