I'm the same way: take a question and answer with the source. But as my time gets more and more constrained, I wish more large open-source projects had design docs akin to CockroachDB. I read through the CDB design doc in one sitting, then read the source and it was such a treat to have that high-level context while wading through the details.

I can't say the same thing for ElasticSearch (or most large open-source projects). It's very difficult to get the high-level context without a well-written design doc explaining why things are the way they are. Some parts of ElasticSearch make sense, and other parts just seem hackneyed. Of course, I could pull together little bits and pieces of high-level insight from multiple disparate blog posts and forums and mailing lists here and there.

But what I would like is a design doc! If you were to produce something along the lines of that for open-source projects that need it, I wouldn't hesitate to pay a modest fee.