It's a fair point that specs evolve, and that sometimes includes deprecation. I do feel slightly aggrieved about the `scoped` style attribute being spec'd, implemented, and then dropped shortly thereafter.

But overall I feel this approach has worked well over the years. With jQuery for example, I only learned enough to get by working in those codebases, but I committed to internalized all of the standardized DOM methods and Array methods and naive XHR workings. Now in these modern times, jQuery still _works_, but whatever I came to know of it is no longer very useful to me, day to day.

Deprecated HTML tags are relatively rare though, especially more recently. You can pretty much categorize every one of them into tags that are purely concerned with styling, frame support and applet type things. And in all cases, the deprecation took a long time, long enough that it would outlive most apps.

And nowadays, even if dialog happened to be deprecated, you could always continue to support it using a custom element if you really needed to (which probably wouldn't be the worst approach even if you were building it from scratch, to be honest).