I don't mind Drew or Fabien's layout, which have a reasonable column width. But Dan's site is unreadable for me (at least on desktop) without reader mode. What would be the reason for choosing to have full-width text on a blog?
I wouldn't mind resizing the browser window except that with tabbed systems that means you're resizing all of the tabs at the same time.
I tend to think that if you make the width something in the neighborhood of what the NYT, Medium, or other well-known sites use, people won't complain. But I could be wrong!
Cumbersome, but one can change width of a single tab by using the inspector and using the responsive design mode.
Perhaps there is room for another Firefox feature to limit width of a page. Perhaps multi-column mode, where one can for example split the page in 3 columns and each column displays, what could not be fit on the previous column. And resizable columns maybe.
Back when I used an OS that didn't let me scale the UI, I'd occasionally make the browser window narrower to make the lines of text on a site more reasonable, but I definitely appreciated it when sites made it unnecessary for me to do that, by specifying body {max-width: 45em;} or something.