That doesn't solve the problem, it just pushes is down the road a bit. The exponential growth is merely offset by a constant factor once. Unless we figure out how to push transistors in the 5th, 6th etc dimension with every new generation.

It was never a solution, Moore's law has more than one dimension as well, not just density but heat dissipation. Can't cool down a transistor that's surrounded by transistors on all sides.