I really wish people would actively avoid the fancy JavaScript SPA approach. (And I work on such an SPA.) There’s a place for them, but this is not a good demo of that place.
Or just have a button somewhere for a "basic HTML" version.
Why are modern developers and UX designers so averse to giving users control over their experience?
Honest answer to your question: Because they have to-do lists a million miles long, and "make an HTML-only version" is often at the very bottom of that list, because it may require high investment while providing few benefits relative to other things on the to-do list. Also, because "giving users control" can mean a million different things… colors, fonts, sizes, dimensions, HTML vs JS, etc.
I agree with your point (here, have an upvote), but really, this should be, and already is, a browser option. Easier to do that than to get thousands of web sites to change. I know Safari has "Disable Styles" and "Disable Javascript" tucked away under the "Developer" menu of all things. Firefox has a "No Style" option somewhere in View. Would be better if it were easier to get to or even the default.
