Earlier quoted context omitted.
I don't think you are understanding the parent correctly. They are saying a person with a partial visual impairment can still benefit from a well-designed visual page layout, because a person with partial visual impairment might still use vision in some ways. So well-designed CSS and images DO benefit those individuals. You seem to be implying that anyone with a visual impairment, even a partial one, would prefer to…
What does that have to do with accessibility? > You seem to be implying that anyone with a visual impairment, even a partial one I am not. Well written CSS, a subset of usability, is irrelevant to accessibility.
Says who?
https://www.w3.org/WAI/fundamentals/accessibility-usability-...
> There is a significant overlap between accessibility and usability. ISO 9241-11, defines usability as: The “extent to which a product can be used by specified users to achieve specified goals effectively, efficiently and with satisfaction in a specified context of use”. This could address accessibility when: “specified users” includes people with a range of disabilities, and “specified context of use” includes accessibility considerations such as assistive technologies.
Let me give an example: If I put icons on my buttons to improve the usability of my app, but the icons break at high zoom levels, then is that accessible? No, but you'd never know unless you do accessibility testing with CSS and images turned on.