Sam Wilson
The 'abandoned:' key should be used for features which "still have some physical form reflective of their former use visible in the landscape.", see https://wiki.openstreetmap.org/wiki/Key:abandoned:

I've added it there (as `abandoned:highway`). And yep, I totally agree that the geometry of the thing should stay on the map (at least as long as there's some trace on the ground of the former track).

Features that are not present in the landscape shouldn't be mapped, and all metadata should reflect the current state and usage of a feature.

I totally get the desire to map everything, by the way! It's just that OSM isn't always the most suitable place. You might be interested in https://openhistoricalmap.org