The new MDN design looks snazzy but no longer works in NetSurf. I would hope a resource like this was highly accessible, even to browsers without CSS3 support (isn't this why we have @supports?). It's also furthering a trope of themes being a binary toggle; there are more options than just white and gray--how about OLED black to conserve the least about of power (looks better on my screens too).
I agree that pages about web development should themselves not depend on CSS3 support at the renderer because it's a huge step forward from CSS2 and the documentation itself is just simple documents rather than complex layouts. This has the air of web designers not having even considered this aspect and just went with modern web standards as usual. So an issue should maybe be raised about this. As I browse the site, it's rather simple, strongly text-centric layouts here that may be assisted by CSS3 at places but I can honestly not see why there should be a desperate need.
The content of MDN is open at https://github.com/mdn/content, currently a mix of HTML and Markdown but getting transitioned to Markdown. So a different effort could perhaps be made here for a "low-tech" (like CSS2 at most and Javascript-free?) static page generation to live in parallell with the modern pages. It's all neatly organized in a hierarchical structure.
Actually one could use the latest on the edge modern web standards for this, but leverage graceful degradation so you still have documents that are both readable and comfortable in a browser supporting less things.
If there is one set of standards that would allow that, it's the Web!
This kind of documents should be perfectly readable in plain HTML without CSS and Javascript;
Instead of creating a new tool to convert MDN's content into HTML, it would probably be easier to modify the official tool, Yari, in order to produce web page with more compatible (and faster) CSS & JS.
https://github.com/mdn/yari
But I don't think it would be useful unless MDN merges in the changes. My daily web browser struggles with the new MDN rendering unless JS is disabled. So I've lost a few features since the "design change", notably I cannot run the examples. Would I use a cloned site that's faster and where CSS&JS are more compatible? I would loose the external search I'm used to (DuckDuckGo !mdn), so using the clone would require a few changes on my side...
