How to Get Feedback From the People You Manage

I think what took me by surprise is how difficult it is to be a people manager while not being a work manager. So that's my case. I do not manage the work of people. Each of them have the work, and then I also have my work as an individual contributor. It feels a little bit like tricky to evaluate a person that has some control of certain things even if Kim seems as small as approving holidays.