Dont make me laugh we can hardly design a workplace that’s efficient for people. Its just that humans can adapt easily to solve all kinds of problems.
Redesign it from scratch including non humanoid robots from scratch is a huge complex endeavor and a big risk. Its much simpler to build a factory like usual, buy off the shelf humanoid robots that can in case of issues easily be replaced by human workers. Profits are more guaranteed.
We can definitely create novel narrow use robots with maximum efficiency but capitalism prefers mass produced one size fits all solutions.
You also dont need to operate humanoid robots. At least thats not the ideal use. The goal is full automation of what is now human labor