I mean, that thinking is obviously wrong. Not everything is within your manager's power to fix. And people have different tolerances with how many headaches they put up with too. The manager might need much more time to improve things than their employee might tolerate.
Those are good points, but at the end of the day, people issues are management issues. It may not be your specific manager that is responsible but the management of the company and HR, who are responsible for the work environment that is set. I'd imagine it is a business (think money) decision on how much time and effort is put into cultivating a reasonably tolerable work environment. if employees have unreasonable demands for their work environment, I agree, it is the employee's fault. But fault aside, even for unreasonable and overly sensitive employees, they're still leaving managers who can't or won't fix people issues in their teams, more often than not, with many many exceptions of course.
If by "people leave managers" they mean anyone in the chain up to and including the CEO, then I guess? That's hardly a meaningful statement though, it's practically a tautology... the CEO is ultimately responsible for everything the company does, so whatever reason you have for leaving is their responsibility... by definition. I can't say I find a tautology like that to be a particularly insightful observation, but maybe I'm missing something.
Let me put it differently and talk about immediate managers only. If the people problem is coming from other teams, the immediate manager should "shield" their team members from that. If it is between their team members, then they need to somehow manage the person reporting to them. They can't always, and I personally find that understandable. But still, the "people leave managers" expression is implying that either that manager is not capable or they are not being given enough resources, authority or training to manage people in their team and outside their team.
From the CEO down to line managers, management is responsible for setting the tone and culture. Jeff Bezos and Tim Cook alike are responsible for how horrible and toxic of a work environment exists at amazon and apple. If the company is great, employees can usually switch teams when they don't like a manager.
Yeah, the "managers" in the term "people leave managers" refers to their immediate manager in my experience, and often their immediate manager doesn't make the call on a lot of stuff.
I'd say they leave people. The people aren't necessarily managers.