This is even better, in my opinion: https://bestmotherfucking.website/

Anyway, I agree. Text should always have a max width. Long lines of text aren't really readable.

I use this in my SurfingKeys settings, and use it on a lot of sites to make them more readable:

  mapkey('<Ctrl-m>', 'Centers the current page', function() {
    document.body.style.cssText = "font-family: sans-serif !important";
    document.body.style.cssText += "color: black !important";
    document.body.style.cssText += "line-height: 1.4 !important";
    document.body.style.cssText += "margin: 0 auto !important";
    document.body.style.cssText += "max-width: 60em !important";
    document.body.style.cssText += "background: none !important";
    document.body.style.cssText += "background-color: #FEFEFE !important";
    
    return true;
  });

For a long time I used to just disable CSS in Firefox (View, Page Style, No Style), which gives a readable page most of the time. I knew about Reader View, but because it only allowed low contrast gray text, and because I already had a workable solution, I dismissed it at worthless.

I recently noticed that I was using No Style so frequently that it would be worth checking for a better solution. I found it's possible to fix the low contrast text in Reader View with custom userContent.css:

    @namespace url(http://www.w3.org/1999/xhtml);
    @-moz-document url-prefix("about:reader") {
    body {
      background-color: #FFFFFF !important;
      color: #000000 !important;
      }
    }

No Style is still occasionally useful to get something readable where Reader View fails, but now I use Reader View most of the time instead.

Have a look at the Chromium/Chrome's extension Just Read

before / after https://i.imgur.com/Ihy5wQh.png

It takes less than a second to Ctrl-+ a few times until the site becomes extremely readable.