> Every single website on the internet always was, is and will be HTML (with various kinds of XML/SVG markup sometimes). People just gradually realised proper and standardised web design makes the Web better for everyone, by making it more usable and accessible.

Unstyled HTML (optionally with user style sheets) is more usable and accessible than today's one-size-fits-the-designer design for the kind of content that used to dominate (and is still a large segment of) the web. (We've got better tools for making usable and accessible content, but they are mostly not used for that purpose.)

For interactive applications, its a different story.