Having been in on the company's leadership meetings where departures were noted with a simple 'regret yes/no' flag it was my experience that no single departure had any effect. Mass departures did, trends did, but one person never did, even when that person was a founder.
The rationalizations always put the issue back on the departing employee, "They were burned out", "They had lost their ability to be effective", "They have moved on", "They just haven't grown with the company" never was it "We failed this person, what are we going to do differently?"
Now an individual manager might do some introspection, but even then the change impact of the departure is insignificant compared to the change that can be wrought by being there and honing your persuasion skills.
That's been my experience in academia as well: any person leaving can be rationalized somehow, and only individual staff personally invested in that person tend to do any introspection about what could've been done differently. Multiple departures can cause a shake-up, though, mostly because the higher-up administration that usually ignores such matters may feel the need to investigate if a trend seems to be developing. Of course, if the problem is the higher-up administration's own policies, that doesn't help, but it can help if the problem was unnoticed malaise in a department.
The rationalizations always put the issue back on the departing employee, "They were burned out", "They had lost their ability to be effective", "They have moved on", "They just haven't grown with the company" never was it "We failed this person, what are we going to do differently?"
Now an individual manager might do some introspection, but even then the change impact of the departure is insignificant compared to the change that can be wrought by being there and honing your persuasion skills.
And given that, the exit interview is a nop.