I think you have that backwards - but there would always have been exceptions.
Yes, in general, the old Cruise Personalizer way of choosing Early or Late TD, or Anytime, meant that in most cases, the TD would get full and folks would have to WL and then be in AT dining.
Even if the trend has shifted, reducing TD from nearly 50% of the space/time down to 1/3 doesn't seem unjustified