As much as I hated my last job, I thought my boss' job was even worse because of all the corporate BS he had to constantly put up with. He seemed to love his job despite that, though.
Also, some of my colleagues (who'd been working for decades, just like me) seem to still love it and thrive on the stuff that made me want to quit and demotivated me. I'm fascinated with how some people like them are able to persevere and thrive in the same situations that make people like me quit and burn out.
I still don't know their secret.
What's amazing about corporate is that, when you get together years later and the truth comes out because everyone has moved on, you realize how much everyone really hated their jobs. There are some true-believing useful idiots out there, but I'd guess that 80% of people see corporate for what it is--they're just not allowed to make it known that they do. It's reminiscent of that time people applauded Stalin for 11 minutes because no one wanted to risk being the first one to stop clapping.
As a worker, you're at least allowed to grumble a little bit. As a middle manager, you're a full-time actor. You have to implement the will of some truly awful people and pretend to have no moral objections whatsoever.
Some middle managers truly are pricks and petty tyrants, but my observation is that most of them are just forced to pretend to be that way, becoming the face of horrible decisions so the execs can be loved by the masses. Your boss doesn't want to be a micromanaging cunt--he has to pretend to be one, because he's a rubber glove for executives.
I think companies really need to work on reducing or eliminating the amount of bullshit ICs have to deal with vs management (time tracking, status updates, on call, etc) or have management do the same amount of bullshit. Your boss may say they understand what you're going through, but they most likely do not have the same level of bullshit being asked of them on a daily basis. They can sit in meetings all day, miss deadlines, and no one knocks them on it like an IC where being a day late gets put on a PIP.
Every company has an invisible line, like the officer/enlisted distinction in militaries, but always undocumented for obvious reasons. Above it are the real humans whom the company cares about; below it are the "resources". ICs are always below the line, except in R&D jobs that aren't available without a top-10 PhD... but most managers are also below the line.
Above the line, you basically write your own performance review because the bosses are your buddies. Below the line, it's miserable, and as you said you're one delay or mistake away from being sent to the Performance Improvement Camps. Almost all first-level managers in a company of significant size (25+ people) are below the line and spend just as much time on humiliating work justification (e.g., status reports) as the guys at the bottom.