Compare this to a human brain which too, has a sulcated layering system for the grey matter but the white matter connectome turns it into a fully three dimensional object. We can't produce such a thing with technological means yet.
The CPUs we produce have to be deployed in datacenters and computers within distance to each other, mostly for heat dissipation reasons. We can't just stack $N CPUs onto and next to each other until we reach an object of the size of a brain. It would not be practical to cool that thing. Compare this to human brains which require much less energy (20 Watts on average).
Moore's law is dead but it's about size of transistors. Human axons have diameters of hundreds of nanometers, even the gap of intracellular space of a synapse is approximately 20 nanometers. Compare this to the 5 nanometers we got now. We don't need size improvements to model brains, we need power consumption/heat dissipation/electric loss improvements. Also, CPUs are still very expensive. We also need improvements in manufacturing them more cheaply. Both isn't really requiring node sizes to shrink further.
Sadly, there's a different law called Dennard's Scaling which was precisely about power consumption, but it has been dead for about 13 years. https://en.wikipedia.org/wiki/Dennard_scaling