The ADA only requires reasonable accommodation. The ADA does not need to be changed to "protect the disabled". That's silly. There are plenty of places where access is unreasonable for certain disabilities. For example, if you can't walk, then you can't get to the crown of the Statue of Liberty.
If you want to get to the bottom of the Grand Canyon, it's unreasonable to expect the National Park Service to provide you any help. For a price, you can get a private contractor to take disabled folks down on a pack mule:
Mules used to Pack Lazy, Sick, Weak, Old, or Handicapped People into and out of the Grand Canyon
These are some of the Mules that are used at the Grand Canyon, in order to Pack Lazy, Sick, Weak, Old, or Handicapped People into and out of the Grand Canyon. They have more than 200 Mules.
What's reasonable is the key. The fact of the matter is disabled people are going to have to spend extra money, get special equipment, hire special helpers and make special plans to do anything and everything in their lives. They don't need the government to do it for them. There is no elevator at the Grand Canyon to take people down to the river.
"Through the years, more than 600,000 have ridden mules in the Grand Canyon, but not all on the trails used today. The first of many entrepreneurs to offer mule rides in the canyon was Captain John Hance, the first white settler at the Grand Canyon, who began his business in 1887. Today, Ron Clayton offers the service to Grand Canyon visitors. Clayton's pioneering efforts in offering mule rides to the disabled -- including quadriplegics, blind people, and double amputees -- has earned him the 1998 "Horseman of Distinction" award from the North American Horsemen's Association."
Please notice that in the example that I gave concerning the Grand Canyon that lazy people are included. Even perfectly healthy people can use the service. It's a reasonable accommodation that is available to all, for a price.