Unfotunately, it’s the teachers union that keeps ignorant and incompetent “teachers”. Teachers should be teaching kids to be learners, that was the idea of the classical education, to give people the skills to educate themselves throughout their life. Not to insure that someone had tenure.
You seem to ignore entirely that the teachers in most cases are doing exactly what the administrator want them to do.
It is a myth that administrators can't fire teachers, they don't have to, they just make their duties so bad they can't take it and they leave. Besides they don't want to fire the teachers you detest, they want to fire the teachers that think like you do.