Accessibility is not just about vision-impaired users. It is about making your website accessible -- to anyone.
JS websites without fallback reduce accessibility for:
* Users with slower devices
* Users with dated devices and browser software
* Devices with poor connectivity
* Users who have JS disabled through no choice of their own.
* Users who choose to disable JS.
* Browsers which do not support JS.
* Accessibility software.
* Not to mention bots, scrapers, etc., who also have valid use cases.
This is a non-comprehensive list I came up with in just a few minutes. I'm sure there are many more items that can be added to it.