I hear you! Managers can be bast@@ds. I've met a few good ones, but most love the power, they're usually the loud, confident ones whose face fits, desperately trying to prove their worth / role.
I've been teaching nearly 15 years, mosly successful, but have been driven mad by the book looks, micromanagement, increasing poor behaviour, ridiculous workload, constant lesson observations with managers nitpicking about things that they don't do themselves. And you know what's dam annoying, is being picked up on something by a manager, just to prove their worth, and they DON'T do it themselves! "Two of your children didn't underline their dates in your lesson today. Please make sure you lap the room to check". Yes, I will fly around the room like a tornado! Then I sneakily looked at their books in their class, and what do I find, some dates not underlined!! I just can't stand the unfairness.
You're right, it's too easy for one manager to form an opinion. It's too easy for a manager to force their opinion on you about how to teach a unit of work and how to plan it. So many great ideas I have had about how to teach an English unit, only for a a manager to step in and change it for what they want. They are all sheep in schools, all following each other. You're lucky, if your face fits. Otherwise, schools are generally very unpleasant places to be, staff trying to outdo each other, each trying to impress the boss at the expense of someone else. Then there's the lack of money for SEN, the lack of resources and so on.
I've had enough. I'm getting out and will be part of those awful statistics of so many teachers leaving the profession.