The documentation is very good covering 'What does this command do' but mediocre to poor on 'What are the ramifications of this' and 'How do I accomplish common tasks'.
A good example is creep parts. There is precisely no coverage of 'how many move parts do I need for different situations' or 'how much claim is enough' or 'what does my creep cost per tick' or 'when is it worth it to boost a creep part'. Answers to all these questions require a lot of math, spreadsheets, or experience and none of it is explained in any documentation despite being critical information for decision making.
It can all be derived from the given information, but that's not the same as being explained. There are many systems in the game that have no explanation of how they work, and no intuitive understanding can be made without doing math. This is in contrast to other RTS games that draw on real life to provide context and intuitive understanding of the relationship between units. Because we are require to build every unit ourselves from scratch, but are given no context about what makes a good unit for different roles, it's a serious sticking point for new players.
Programming is difficult... programming when you don't even understand the system requirements is much harder. The documentation does not provide a surrogate 'expert user' to get domain knowledge from. It should.