Do you remember coding rounded corners in HTML? Slicing images, putting a 3x3 table with rowspans and colspans? That was easier than `border-radius: 3px`?

And I have seen no solution for how we might code responsive layouts in pure HTML.

Your making a lot of assumptions, but to be pedantic strait text + links is both pure HTML and a responsive layout. Sure CSS is useful, but IMO most of the pain from HTML / CSS / JavaScript is trying to recreate native application's pixel perfect layouts in a webpage. Also, I think you can embed all CSS functionality into strait HTML5 the advantage is CSS is concise not necessary. Granted, not something you want to create by hand, but if your code is generating HTML anyway it's not such a big deal. EX: <style>

In the end CSS was designed to allow you to swap CSS styles independent of the underlying HTML not add new functionality to HTML.

> strait text + links is both pure HTML and a responsive layout

It's a responsive layout, but not one that somebody is willing to pay me to build. Those that people will pay me for are, in my experience, easiest to build with CSS.