Actually only partially true IMO.
We have rented a car because of certain activities for certain trips.
If we have a Clearwater stayover, UNI actually 2 days once, and the Citrus Bowl or once a Spring Training game in Ft Meyers we have rented a car.
But we still used ME because the bags show up in our room. Its just easier. Then we also checked out on our last day and sent the bags home on ME and then drove to MCO.
Otherwise we usually cab over to UNI during our stay.
ME didn't at all keep us on property those trips. At least for parts of our stay.
Now what does keep on property is FP+ and WDW night shows and
DVC.
Coming back even from UNI we always hit either DHS or MK for 3 FP+ and either Fantasmic and Star Wars Fireworks or Wishes CTM and parade. Then walk over to BLT or BWV or BCV depending where we are at.