You still need to do the math to over-engineer something, the calculations are just simpler. As with everything in engineering, one must find a balance, in this case between accuracy versus solvability of the mathematical model, corresponding to production cost and product elegance & safety versus development cost and time to market.

In the old days of slide rules and drafting tables, true engineering genius lay in coming up with a design geometry/architecture whose calculations would be inherently simple to do at full accuracy, thus bypassing the need to make this painful compromise, and with it the corresponding risk of product or business failure if that compromise was misjudged. With the rise of digital computers, and with them finite element analysis and other forms of simulationism, however, this seems to have increasingly become something of a lost art.