I think webpack is a special exception. It somehow revised the whole 5 major version and still don't get a proper plugin development document at all, not even basic one. You don't even have a flow graph that tells you events happen in which order. Everyone either Google and copy paste random example or reading the source by themselves.

It always amazed me that such a big project can just live without docs.

that's the only thing agile people got from the manifesto

an excuse not to write docs, ever

it's endemic in the majority of companies I've seen in the last 10 years

hopefully tooling (eg. docs.rs mostly automatically generated and pleasant to use) will help in the long term