If you are teaching people, I expect you to be smart. I expect you to be very skilled at doing what you are teaching and at being able to identify errors that your students make and explain what they are and how to fix them.
But the mark of an amateur teacher is talking too much. You may know everything that's wrong and you may be able to explain how to fix it, but talking will not make students get better. Students have to practice. They have to make their own connections. If you are always stopping them to discuss their issues rather than having them repeatedly work to correct them, they will make far less progress.
With writing specifically, consider what has helped you to grow the most. Was it talking about writing, or was it actually writing? Talking is good in theory. It gives you things to consider, ideas to explore, but it is when you are actually putting words on paper that you are seeing first-hand what works and what doesn't.
Most importantly, writing is a long process. You need to bang out a whole draft just to know what you're doing and where you're going. There basically is no reason to even discuss a story until you have your first draft done (and maybe not until your second one). Anything more than that will just be micromanaging. If you want to be a great teacher, know when it is best to stop talking and let the students teach themselves.