No mention of the element [1] but that's probably because browser support isn't great—not implemented in Safari, experimental flag in Firefox. The lazy-loading option for img elements is news to me, but I think I'd still prefer to use JavaScript for that task. Same probably goes for the dialog element actually now that I think about it. Having a simple HTML5 option might seem cool, but I like to keep the actual logic…
I prefer to depend on the user agent for user interaction and behavior. Javascript and all its potential for tracking, malware, side channel exploits, etc. should be abolished from the safe web.