The entire industrial revolution was steel replacing human workers. And that is still the backbone of the world today. We are still living the industrial revolution.
Just like the invention of fire happened ages ago, but is still a crucial part of life today.
No, it was actually engines.
The mechanism behind engines were fully understood, any experiments with engines were reproducible and measurable. You could get an engine and create schematics by reverse engireening it.
LLMs, useful as they may be, are not that.
Famously Andrew Carnegie spent years trying to get the steel to stop talking about goblins.