Agreed! During my years of Army life, I to had been an instructor. Not a very good one. Some (actually most), were very good. None had any teacher's training. It seemed that those who had the knack for it, were really good right from the start. Others, no matter how hard they tried, no matter how much assistance given, just couldn't cut it.
Anyway, from what I've seen raising four kids, the same was true in public schools. There was that upper 10% who I would have graded super teachers, then their were the next 30% who I rated not good, not medicore, but poor (barely adequate). Then the next 30% were really bad (total failures). Then the last 30% who didn't belong in the school building.
The difference between the two, was that in the Army, other duties were found for seargents who didn't cut the muster. They still had duty assignments in their military occupations. In the schools, they just keep right on teaching.
Part of the problem is that too many teachers never leave school--they graduate high school, go to college, graduate college, then go right into teaching.
In other words, they are a poor role model. They have no life's experience, or accomplishments to draw from.
It's also easy to talk theory, but putting theory into action often reduces pure theory into ashes. Young teachers are often great at figuring where social injustice lies and how tax dollars should be spent, but they haven't figured out that, generally speaking, people are where they are today because of the choices they made yesterday and that they will be tomorrow because of the choices they make today. They also don't realize what it takes to make a buck.