You're also making a lot of assumptions about me but I'd rather not make this anecdotal. I would have probably agreed with OP when I was 18 after watching Fight Club a hundred times that was what modern business life was like. But I've had a large variety of jobs in my life from working outdoors, brutal factory floor jobs in an auto factory and a wood flooring plant, to office-space style boring corporate HQ jobs for a big brand, to tech companies for the last decade and it's hardly the standard. Especially once you get past lower level drudgery work.

I already mentioned it'd be stupid to put that level of sacrifice into a company unless you were adequately compensated or given enough power/time to accomplish actual culture change. And of course there are modern bigcos who are borderline dystopian where it's impossible or SMBs with sociopath leadership who doesn't want change. Which is when you leave if you can't tolerate the environment, assuming you can, but attempting to change it is a whole different beast.

I've also been a manager at a company with a shitty culture, and you simply can't stop your good employees from leaving for greener pastures. You're kind of happy for them when they do. I care about my employees and value them as human beings, but I also couldn't address their grievances or promise them any resolution to larger cultural issues. I knew they would leave, so I stopped being upset when they did and started taking the turnover as part of the job.

It's not that managers don't care about their employees, they just don't care if or why you left because those circumstances are outside their control. HR collects that info in exit interviews, and a line manager has no influence with HR. If turnover starts hurting the company's bottom line, they'll do something about it. Otherwise it's not going to be a priority at the levels it needs to (how effective is your "Diversity Officer" in creating real diversity?)