Most of it isn't.
The wins I see most often take minutes:
— Describe your images, so a screen reader says something useful instead of "image"
— Raise the contrast on grey-on-grey text, which everyone struggles with in sunlight anyway
— Let people reach every menu item with a keyboard
None of that needs a redesign, and all of it helps customers who'd never describe themselves as needing help — anyone outdoors, on a cracked screen, or in a hurry.