Why would it be at odds with accessibility? The text contrast is excellent in each section, and the light/dark segments clearly define the border between sections. Forced dark mode can be difficult to read for users with astigmatism, but the font size is large, and the actual documentation sites[0] do have a light/dark switch.

[0]: https://elixir.hexdocs.pm/1.20.2/

I have zero astigmatism and dark mode is hard to read as letters look all blurry.