Great observation, that most tasks are context depended in terms of a specific location. Immediately more of these contexts or pre-conditions pop up in my mind: social circle, mindset, internet connection, ... Thinking about this more, there seem to be 2 different types of conditions: some that have to be met once sometime before doing something and some that have to be met continuously to be able to do something. Maybe one could connect a system that creates location/time based reminders for steps with pre-conditions. What do you think?
When it comes to the 80%, I'd agree with you if "the job" is defined as "getting relief from the complexity in the moment". I'd rather define "the job" as having a system that you can trust and rely on for a prolonged time. Then a piece of paper is not cutting it, based on my experience - its too expensive to make changes.
I do agree with your attitude of better writing things on paper with the simplest imaginable structure than not structuring things at all.
If things are so individual, probably tags are the way to go. You could then have a auto-generated step containing all steps with a particular tag. Logseq and Tana actually have such query items. In OmniFocus I've seen a hierarchical tag structure which looked pretty useful.