You may feel like not adding much value because you may be measuring yourself by the wrong metric. If you are / was a software developer, its kinda easy to see your contribution, you just pull the git log. When you are leading, its way harder to notice. Thats the jump to the soft skills.
I like to think soft skills are called this way because they have a soft touch. You cant really define what they are, but you know when you are not having it, much like clean code.
It seems like you know where they can develop and get better. Managing them is helping them achieve it. Help them, guide them, nurture them. And mostly important, ask them where you can help.
Being the manager is not being the smarter, just the facilitator. You make thinks smooth. Managing is good when you cant see and it feels it does not exists, but, you know things will be worse if the managers are out.