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).
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).