I want to talk about documentation. iOS1, Nginx, Python, DRF, Django, Celery, and Postgres have excellent documentation, but documentation only helps when your question is "How does this thing work and what does it do?" Documentation, at least code level docs, are useless when it comes to figuring out what you need in the first place. Celery can tell you how to use Celery, but it isn't as great at telling you why you might need it. I've become convinced that user guides are as, if not more, important than code level documentation, and we as a community need more of them.
1. For their credit, iOS and really all of Apple's developer resources have excellent user guides that explain not only how to use a thing, but why and where you might need it (thinking about it, this could be because iOS and macOS have been around long enough to develop these kinds of docs).