This is Amdahl's law in action. [1]

Until we figure out a good way to leverage humans in all of this ("Attention is all you need" applies equally to humans as it does to models) productivity gains for the system will always be limited by Amdahl's law. Gwern has an excellent post on this. [2]

[1] https://en.wikipedia.org/wiki/Amdahl's_law [2] https://gwern.net/guardian-angel