So for fun I did a thought experiment to help me determine the most essential gear for my AM commute under two different scenarios: Winter and Summer

For both I start with my de-accesorized (i.e. 'naked') bike, no bottle cage, no lights, no speedometer, etc. and with totally naked me.

Scenario 1: Winter, dark, 25F
I, totally naked, jump on 'naked' bike. It would not be safe, but even without lights I probably could make it to work with extra care and acting as an 'invisible' cyclist, giving up ROW even when I had it, jumping on sidewalk in presence of others who can not see me as I am unlit, etc. It would quickly become painful. The cold would hurt. My bare feet on my clipless pedals and stepping on cold rough ground would hurt until the numbness took over. Perhaps some bleeding and begininging of frostbite. But I could make it to work. Now I consider what one item would help the most. I think it would be shoes. They would help protect my feet from the cold and physical contact with pedals and ground.
Conclusion 1: In winter shoes are the most essential item

Scenario 2: Summer, daylight, 75F:
Again, naked me jumps on 'naked' bike. Again I could make it to work. I could ride more normally relative to winter as lights are not needed. My bare feet on clipless pedals would hurt some, but nowhere as bad as in winter. Here the most likely thing to prevent me from getting to work is being stopped by police as in the daylight (unlike in the winter scenario) I would clearly be seen as naked and even as I don't pass police on the way to work often, surely someone would call it in to the police and they would quickly find me and I would not make it to work. Bike shorts would prevent this.
Conclusion 2: In summer bike shorts (or equivalent) are most essential

Al