It's just that nobody wants to make a Win32 style app with absolute positioning on the Web. That's because responsive apps are superior to nonresizable, manually positioned UIs.
But it doesn't solve the problem with high DPI, changing fonts, and localized strings being sometimes significantly longer, requiring widgets to be resized to accommodate them.
When I click on some languages (I am not native English and my native language, Dutch, is not very high on the list of priorities for most companies) in some of the biggest companies in the world, you notice it just wasn't designed for that. From just making it wrap and enlarge to break the design to simple sticking outside the box.
For some localizations (Chinese for one) you will have to redesign anyway because 'our' (not sure how to describe) designs simply do not work/sell over there.
Most global companies have a local presence doing their local sites; I know some, even inside the EU, very big companies that have a site per country and have the html/css look 'the same-ish' for the user but completely different when you check the source to accomodate for local taste / language.
I like the dream of this working, as I am a programmer, but I don't see it in real life and I find html/css just painful to work with; not difficult but painful compared to most desktop GUI tech. Flexbox etc is changing that a bit but still it looks like people are shoehorning everything in this html5 stuff just because they desperately not want to use/learn other things instead of using the best tool for the job.
Disclaimer: I am old and have seen this before. I do create webapps and use React (new license makes it workable outside hobby projects), but I will gripe about it like the author of the blog post.
It's what I imagine a reasonable HTML/CSS would look like.
