Exactly, and that is what underlies most of the issues.
A tagging scheme to describe all the variations, excellent. But that does not answer the data user’s question: if further descriptive tags are lacking, what do I assume, or do I leave it out altogether? Do I take country-specific notions of what a path/cycleway/footway is, and if so, which countries do I support?
I think the way to go is to define a fixed set of OSM-wide defaults for the descriptive keys.