What if the farmer built/tested/refined the pathing/automation around the tractor? I mean it probably doesn't ship knowing the most optimal way to plow the layout of his fields. There's still some knowledge/skill required in optimizing that portion.

The argument does eventually degrade over time, though. For example, in the future the farmer uses satellite imagery fed into an advanced AI to build the most optimal route. So yeah, eventually the farmer loses all utility I suppose beyond being a land owner (until AI owns land lol).