For some examples of modern html, see google's style guide for html, section 3.1.7 shows an example of a complete and correct document that may blow your mind. Also, the examples of tables and lists without closing elements:
> A p element's end tag may be omitted if the p element is immediately followed by an address, article, aside, blockquote, details, div, dl, fieldset, figcaption, figure, footer, form, h1, h2, h3, h4, h5, h6, header, hgroup, hr, main, menu, nav, ol, p, pre, section, table, or ul element, or if there is no more content in the parent element and the parent element is an HTML element that is not an a, audio, del, ins, map, noscript, or video element, or an autonomous custom element.
https://html.spec.whatwg.org/multipage/syntax.html#syntax-ta...
This is so complicated. In the end it's easier for me to close the tag instead of second guessing if I may skip it or may not.