Who's talking about comp? While that's a perfectly valid reason to leave, we're talking about interpersonal interactions between a manager and an IC.

>Most bosses are aware of the issues

This is not about compensation.

Leaving for compensation is absolutely a valid reason. Again, though, the same rules apply. Express to your employer you have received a job offer at X% more, with X improved benefits, and would gladly stay for a match. The worst they can say is no, correct?

Either way, the original conversation was about issues with the employer/manager. Not necessarily compensation.

At least one boss didn’t want me to make him look bad. Even the vp wanted me to understand that any problems were not his fault which seemed like a weird thing for a person responsible for thousands of employees.

Because the mid-level manager doesn’t want to look bad to the VP.

I’d say the exit interviews were politically motivated. Most employees had already given months/years of feedback that was never resolved before it got to that point.

They're typically scheduled during your work day after you've given notice. Why wouldn't you?

IME even if they’re mandatory you can give BS answers that sound plausible but don’t burn any bridges. Of course, you should weigh this with improving your coworkers experience and the value of any stock you may own (a high turnover rate in a knowledge-based industry is generally bad for the business.)

No, withholding pay for failure to participate in an exit interview is totally illegal. They can offer incentives to participate, but they cannot withhold due compensation. Whether you do the interview is optional and up to you, but regardless, you have complete control over what you say during the interview, so you never have to bring up problems. It’s rarely a good idea to bring up what you think are systemic problems during your exit interview; there is usually zero upside for you to vent your feelings, and you could accidentally open yourself to liability and/or to reputation damage with your future employers. The time to speak up about problems is long before you leave, while you’re trying to participate in the solution. The best “stated” reasons to leave are because you found something that better fits your own goals, something that is out of the control of the employer you’re leaving, and not because you’re fed up with their inability to fix something (even if it’s true).