I’m a technical writer for very complex server/client networked products and there’s often no way I can sit down and see the whole system work because 1) they never give me a whole system to play with, and 2) it’s too complex to start out with nothing to read first. The engineers are no better off; each writes his or her own piece and sometimes has no clue how the other plug-ins or components use the data down the line. But that’s not as bad as the fact that often, when I ask, “So when would I customer use this feature, and what for?”, I get “I don’t know. I was told to build a [blahblah] service to handle [IETF spec] protocol…”
I envy tech writers who do refrigerator user guides…