Had another thought on this, something that has changed is that designers now rely to heavily on computer modeling and CAD to the point gut feeling and past lessons get ignored. Any model is only as good as the data it is created from, there is still a lot that could be learnt from the way designs were handled many years ago but they required more engineers and time so in todays rush to the finish line you can see how mistakes are made. We would physically model sub systems and fit instruments such as torque meters and strain gauges to get an accurate picture of the potential design and be in a position to iron out any problems before pre production parts were made, now I believe they use mathematical models and a prayer.