Self-closing tags are an inconsequential issue.

Of actual practical consequence are optional html5 tags [0]. They allow you to write html by hand as easily as if you wrote markdown. Some graybeards even say that optional html5 tags make markdown entirely unnecessary.

Thus, lists don't need closing item tags:

    This is correct html:
    <ul>
        <li> first
        <li> second
        <li> third
    </ul>

Tables become uncluttered:

    Raw html tables
    <table>
       <tr>
           <td> are
           <td> easier
           <td> than
       <tr>
           <td> any
           <td> markdown
           <td> flavor
     </table>

And you can even write the entire document in that style:

     <!doctype html>
     <title>Hello</title>
     <p>This is a complete conforming html document.

No need for stupid html, header, body elements. They are optional!

[0] https://html.spec.whatwg.org/multipage/syntax.html#optional-...