1. There are 37,000 rooms at WDW. No way to allocate time slots to everyone, even it were logistically possible, the land would need to be open 24/7 to fit everyone in.
2) The demographic of WDW guests is totally different.
It works at DL because most people there are repeat visitors, if they don’t get everything done they can come back a month later (when it moves to a virtual queue). And if there are guests who are unhappy with not having enough time, and they’re not local AP holders, there is enough capacity to allocate them another time slot to keep them happy.
At WDW many are once-in-a-lifetime or once-in-a-few-Years visitors. They would be mightily upset if they didn’t get to do everything.
3) DL is only doing reservations for 3 weeks. Then it moves to a virtual queue.
WDW has 3 hours a day EEMH. Those are (in place of) the resort guest reservations. There will also be a virtual queue, at some point.