I never had a supervisor I liked, but I have had ones who knew math, knew how to teach and how to recognize good teachers. They knew their subjects inside out. They passed rigorous tests to get their positions. I never liked being observed but the old ones, the ones that knew their stuff and often ripped me apart, taught me to be a better teacher.
I never thought I would say this, I miss those old supervisors. What can anyone possibly learn from administrator who knows little to nothing about the subject s/he is in charge of and has minimal experience, often in subjects unrelated to what s/he is in charge of ? What can anyone possibly learn from the administrator who got his/her degree with borrowed papers, no books and a degree from the nearest 7-11?