Stop delegating. Start teaching.
On the subject of teaching:
Teaching, of course, is how knowledge is transmitted from one person to another, one generation to another.
But there’s something else going on, just as important: Teaching is also a form of learning i.e. you don’t really know a subject until you can teach.
So if you want to master a subject, learn how to teach it. Easy.
This idea is pretty standard in academe, of course. But less so in business. A lot of managers just expect to delegate, and little else.
If all you do is delegate, tasks get completed, sure, but no deep learning takes place. And deep learning is where the real value is.