The issue is not that there is a simple feature that's inadequately documented. It's that I have no high level understanding of what all the pieces are and how they fit together. Tell me exactly what I'm getting from Apollo that I don't get from fetch. Tell me what caching does, when, how, and how to invalidate it. Tell me about links and middleware. This is a very complex batteries included technology. I don't even feel like I understand where the batteries go, much less what they are doing for me, I'm just copying and pasting code that others have used into my projects and hoping I have about the right amount of stuff included.

Your customer didn't write all the Apollo code. The docs feel like they are written with the assumption that we understand the architecture and goals as well as you do and we just want to do some simple task with it to get started. I fear however that this is fundamentally not a docs problem. It feels like a problem where the Apollo devs didn't start by asking "how can I build something that will be easy for 3rd party devs to use and understand", they started with "oooh that would be cool". Urql feels like it started with a very simple and clear conceptual foundation that provides a clear roadmap for how and where more complex features get attached.

If you can reduce Apollo down to a clear and simple framework in the docs that actually covers everything that it does, then you're golden. I suspect however that the underlying architectural simplicity that would be required for you to do this doesn't actually exist. If it does, you face a docs problem, if it doesn't, then docs are just a bandaid.