You can make a bigger ICE engine (like a container ship engine) and still understand how the whole thing works. Maybe there’s more parts moving but it still has the structure of an ICE engine.

With neural networks big or small, we got no clue what’s going on. You can observe the whole system, from the weights and biases, to the activations, gradients, etc and still get nothing.

On the other hand, one of the reasons why economics, psychology and politics are hard is because we can’t open up people’s heads and define and measure what they’re thinking.