See, there's your problem.The essence of being an engineer, in my experience, is (1) identifying the problem, which in and of itself is usually half or more of the battle, and (2) coming up with the best solution to the problem.
The way I describe the second aspect engineering you mention above is to come up with a solution that is just barely good enough to solve the problem. (With margin of course).
(Of course that depends on how you define "best". Sometimes the "best" solution has the cheapest recurring cost, sometimes it's the lowest NRE, sometimes, it's time to availability and sometimes, but not usually, it's the one that has the ultimate performance.)
B