Why not? Sure, if you are unplanned you won't be able to do as much in terms of going on rides or meal reservations, but that's not anything surprising. Most things in life, you get to do more with planning.
But if someone wanted to take a relaxing WDW vacation, what is stopping them? On days when you go to the parks, you either get FP+ on the spot or wait in lines. On other days, you do the same sort of "relaxing" stuff you bemoan that peopel don't do -- go horseback riding or bike riding or do watersports or golfing or mini-golf or take a carriage ride or go to a petting zoo or just relax at the pool. All things still available at the "Vacation Kingdom". If that was the stuff you enjoyed doing 10 or 20 years ago at WDW, why can't or won't you do them now? What would be stopping you?
I guess I don't understand what the change is that prevents people from having this sort of vacation if they want it. I fully understand that Disney does not promote that type of vacation, but the components are still all there available to be experienced if that is what you like.