This site is quite illegible if your system is set to prefers dark theme.

Yes, copied it in to my scratch buffer to read it, not readable in the browser at all with a dark background. It did then make all the elisp nice to look at.

I clicked through hoping you were wrong, saw the first page, and thought, ah, this is legible... then I got to the code blocks and was completely blinded.

I'm not sure what to tell authors of such pages...