This discussion isn't about screenreaders or accessibility - and there is nothing to suggest that being delivered a mobile version of a site would make it less accessible by default. In fact, speaking as someone with a blind family member who has done extensive reviews of highly trafficked sites - the mobile version is often vastly more accessible than the desktop version of many top ranking sites.

All of that aside, I think you're being disingenuous in trying to strongarm this as some sort of rebuttal to parents comment.

Accessibility features are almost always not worth it purely from a profit point of view. They get added because as a society we decided that everyone should go out of their way to accommodate these users because they have no choice and should not be locked out of life.

The author here can simply deal with it or turn their monitor the other way.

This isn't about them. This is about a guy who chooses to have his monitor vertical. Don't take things wildly out of context in an effort to make it sound like people have made points which they absolutely have not.