Mechanical design does not require knowledge of microcontrollers, but if it is electromechanical design, especially automation design, knowledge of microcontrollers is required. However, modern design is a collaborative design between many people. As long as you do a good job in mechanical design, someone will do a good job in microcontrollers. . Of course, it would be better if the microcontroller can also do it, but it doesn't matter if it can't.