Though I've never used it, I think https://ziglang.org/ is a great example as it explains what makes the language unique, gives a code example right at the beginning, and makes it clear where to find more samples so I can quickly judge the features of the project without having to go through the entire docs.
Maybe this is debatable, but I feel like https://kubernetes.io/ is a counter example. It's one of my favorite tools, but the home page doesn't tell me much. I think I would have liked to see code snippets about Deployments or some sort of architecture diagram that explains what it does in terms of different well established protocols like cri-o or cgroups or something. (Honestly the k8s docs are not so bad - I'm sure there are better counter examples that are super marketing heavy).
You might disagree with my examples above, but I'm still curious to see what other people consider "good" in terms of relaying useful information.
https://www.postgresql.org/ despite being quite technical, these docs are very easy to follow in a self learning format.
The new Angular and React docs are quite nice.