There are many many successful applications. Yes, production scheduling has proven to be "resistant" towards mathematical optimization. But many other engineering disciplines rely on it heavily.

Take for example model predictive control aka receding horizon control.

Control people have always built formal models of their systems. And now they use optimization theory where the systems don't fit the old linear quadratic controller paradigm very well.

You drive a car with traction control? Chances are that some embedded system is solving an optimization problem at kilohertz speed so you stay safe when turning on the road.