I use the dev tools to find the containing element with max-width by using inspect, clicking on the text and then finding which ancestor has the width, and then it's something like

    div.article-text {
      max-width: unset !important;
      width: 100% !important;
    }

which works in most cases. It's totally a pain to have to do on a new site, but once it's done then you never have to do it again - at least until the website does a redesign lol.