Comment by notpushkin

> Take headings, for example: in component-based development, I often don't know (and shouldn't care) what level a heading is in my reusable widget, but I am forced to choose regardless.

We could have used <h1>s everywhere with Document Outline:

  <body>
    <h1>top level heading (parent sectioning element is body)</h1>
    <section>
      <h1>2nd level heading (nested within one sectioning element)</h1> 
      ...
    </section>
  </body>

Unfortunately, this was never implemented in browsers and was removed in HTML 5.1.

https://html5doctor.com/computer-says-no-to-html5-document-o...