It must just be me, but it feels that the site is optimized for mobile browsing. There is very little content and my eyes have to move massively just to read the page. I actually prefer the old layout. :/
Documentation websites actually have some pretty good use-cases to being scalable to mobile, either because people will view documentation on a tablet or phone while developing, or due to people using smaller browser widths when developing to be able to display their IDE or terminal windows next to the documentation windows.
Smaller browser widths I agree
But using a phone/tablet to navigate the docs? Might as well use notepad for coding too, since the objective is to suffer.