The level of effort is minimal. It's not a quantitative definition, its qualitative. Also absolutely in no way shape or form is it anywhere near the level of decision making of a director. Your average director of some low budget B netflix slop is still making thousands of decisions per day, organizing teams, reading and writing documents, going over shot review with DP's. A director is the CEO of a film production, not some ideas guy. They require and utilize a technical understanding of all parts of the production.