Implicit end tags aren’t sloppy at all. Documents using them are completely unambiguous and completely well‐formed, as has been the case since the inception of the language.

In fact, the fact that implicit end tags and implicit elements are unambiguous is why they exist as a feature at all. <td> cannot contain <tr>—the idea doesn’t make sense—so <td> followed by <tr> implicitly closes the <td>. <li> can’t contain <li>, so it implicitly closes. <p> can’t contain <p>, and so on. XML doesn’t help at all here: even if you use a strict XML parser, you can make a construct like “<p><p></p></p>”, and it’ll be ostensibly “well‐formed,” but it won’t be valid HTML.

The XML way of “make everything verbose, even when it’s already unambiguous” was a late addition to the language. And it leads to surprise like what’s visible throughout this thread, such as people expecting <div /> to act like <div></div> when it really acts like <div>.