I noticed already that docs.ros.org has no robots.txt or sitemap, so I bet it’s not indexed by google. I chatted a bit with a friend who did SEO in a past life and he suggested going straight to the google search console to at least see that the site is being indexed at all (which given my test on site:docs.ros.org I think is the case).
I’ve opened No robots.txt, sitemap.xml in the web root · Issue #6039 · ros2/ros2_documentation · GitHub and let’s see if I have any time to contribute