In the day-to-day reality of leadership, part of our task is to match skill sets with jobs that need to be done. I stayed at one university for eleven years, in part because my supervisor was able to find new things for me to do and to learn - in other words, she gave me challenges that were in reach but required me to be fully engaged in the work to do them well. Are you challenging the people you work with appropriately? If you are not, have you set up a culture that allows people to address it individually or ask for new opportunities or training as appropriate to the situation?
It's true that we can't really motivate others, but we can certainly demotivate them? We can also challenge and support them. What kind of leadership are you exercising? Is it more likely to produce anxiety, boredom or flow? What do you need to do to find the right level of challenge and skill for yourself and others? Again questions that only you can answer!
Quote from Finding Flow: The Psychology of Engagement with Everyday Life by Mihaly Csikszentmihaly (1997).