To test for a blind persons ability to render your website a good method is a CLI browser. Neither the blind persons device or a CLI browser will render javascript

I’m no expert in this space, but if free, common, and easily accessible tools render your site readable and usable, I’m not sure how refusing to use those tools would be a claim under ADA.

There are plenty of real ways that sites are unusable by screen readers, using Javascript to download dynamic content shouldn’t be one of them.

Why on earth would you think that? The screen readers tie into modern browsers like Safari or Chrome.