I'm noticing lots of people with both the opinion "I don't think I could work under a boss" and "hierarchies are efficient". But there's a tension between these two.

Efficiency properly understood isn't output per man-hour, it's output per unit unpleasantness. That follows from standard econ definitions of efficiency.

My problem is never having the "holy grail" boss outside my time in retail. In tech, we hear all sorts of stories about great founders and what people learned working closely with them.

I've yet to experience that and at this point, I'm looking forward to being that person. A good boss makes hierarchies work.