Yeah, most browsers do have reader mode now. I honestly don't love them because they're typically not customizable, and are sometimes too narrow for my taste.
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!
Firefox reader mode is a little bit customizable. Font size column width and so.
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.
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!