> The idea is: this advanced civilization has such command over physical technology, that they can effortlessly engineer unnecessary strength without losing any of their designed performance.

Are you sure the idea isn't just "we never thought about it"?

Old cars are sturdy and robust while new cars are extremely fragile and will total themselves at the drop of a hat. That's not because the 50s possessed ancient technology lost to the modern day. We put a lot of effort into designing our cars to destroy themselves under stress. We do that so that more of the energy of a crash, should it happen, will go into deforming the car (since that's easy now!) and less of it will go into deforming the passengers.