Good reminder.
The official Postgres manual instantly comes to mind whenever I think about great documentation. There's just something about the way it's split up, and especially the typical length of a leaf page, that makes it absurdly helpful.
And the fact that you can usually find the exact page you want from Google is nice. As a bonus, if google gives you the wrong version, that page links to the same page for every other version too.
It's a joy.
Documentation of major products has definitely improved. As has tooling for producing and consuming it.
When open source was getting rolling in the 90s I don't remember it being nearly so polished.
Ah, you must not work on a Microsoft stack.
Ha. Although you have to admit even modern MS documentation is loads better than it was historically.
And at least there's some kind of acknowledged API now (even if the first class languages shift with the slightest breeze).
More related to software, I have another rule: read the official documentation first before going somewhere else. Though often less polished than external books, it comes from the creator and it usually worth the effort.