And miraculously base html/css already solved that. There’s a reason desktop UI don’t work on small screens and that’s the same reason you don’t do magazine layout on small books. Html is reflowable because that’s the only way it can work across different screen sizes. But designers like to think their canvas sizes is the norm and do layouts that shouldn’t be done.
I'm with you on the size issues, though I don't see html/css as solving it completely.
At the end of the day people want magazine layouts, newspaper splash styles, postcard type areas etc. I think even novel writers/editors have a "best viewed at" size and layout in mind that gives a perfect pace to their story.
Html/css gives the tool to switch layouts and potentially adjust to make the best of the area offered, but it will probably always be a compromise in the eyes of the more opiniated designers, and auto-reflowing content would be more of a necessary evil.
Even in our field we have traces of that with our recommended line length, method length, bracket styles etc.
