Some people want to, they just can’t yet. Often they don’t have the skills or experience yet. But if they really want to, with enough training and practice they will be able to do the job soon enough. They want to be here. They want to learn. They have the right attitude.
Train these people. Show them. Believe in them and tell them so. Be patient as they are learning.
Get them there. They will be some of your best people.
Of course, once in a while, it’s just not happening. They want to but don’t have the natural ability to do the job. You’ll have to reassign some of them. They wanted to, they just didn’t know themselves well enough to understand their inherent strengths and weaknesses.