What happens is heavily dependent on relative traffic flows.
If it's sparse, not much bad happens, there might be more bad accidents from people assuming right of way. If it's heavy in all directions, people going straight or turning to whatever side of the road they're on will be reasonably OK, while people turning across traffic will have a bad time. If it's heavy on one road and light on another, the light road will be starved of exit opportunities.
Turning off lights certainly isn't a panacea. Anyone who's lived in a city for a few decades will remember junctions that got much better with the addition of lights, and junctions that got worse. Some will recall bad accidents (T-bones and the like) that prompted their installation. Etc.
If it's sparse, not much bad happens, there might be more bad accidents from people assuming right of way. If it's heavy in all directions, people going straight or turning to whatever side of the road they're on will be reasonably OK, while people turning across traffic will have a bad time. If it's heavy on one road and light on another, the light road will be starved of exit opportunities.
Turning off lights certainly isn't a panacea. Anyone who's lived in a city for a few decades will remember junctions that got much better with the addition of lights, and junctions that got worse. Some will recall bad accidents (T-bones and the like) that prompted their installation. Etc.