But does this mean that technology has reached its limits? Certainly not in a physical sense. Regarding design capabilities and the issues you raise --

1. Hard problems have again and again been solved through the growth of scientific knowledge.

2. Evolution demonstrates that hard problems can be solved with no knowledge at all, given enough persistence. (Evolution with a result in mind and with higher-level representations of subsystems can be much faster than the biological way accomplished.)

3. Although intelligence is far from understood, manufacturing -- even at the molecular scale -- is in a different category. The problem here is a need for tool development and filling in details, not a need for new basic concepts.