"Hierarchy is so baked in to every other company, organization, and education system that people just don't know how to operate absent it."

That's partly because it works. It is proven. It is well-known. We have excellent tooling for it. There is absolutely no need to change it. Changing does not bring any advantages. You cannot point to any company and say "That company was an outstanding success because they were flat and rejected all hierarchy." If you run a business then do you want to make a political point or do you want to make a profit?

"There are examples of stable large companies with flat org charts that do work, they're just not the hypergrowth scale-ups."

So why waste any time with them? What is the advantage? What is your real motivation? You seem more focused on some political agenda than you are focused on making a profit.