It's been a while since I've used Ruby for anything serious, but I think most people still use https://ruby-doc.org/ for the official docs. What you linked is the site generated by rdoc, which has never looked very good.
What visual thing?
Re:Astonishing Performance of .NET 5
by manigandham on Thursday November 12, 2020 @12:36PM
(#25072269)
Light skinny fonts that are hard to read. The absolute opposite of how text on a documentation site should be.
Ruby's site even does that visual thing where you can tell it was made only to be seen on Macs.