I've worked for good-if-flawed employers who really did need an exit interview to understand what was going on.

In one job, my line manager had gone to a promotion elsewhere, and my manager wasn't in a position to promote me, so her last instruction to me was to spread my wings elsewhere. I handed in my notice on the new manager's first day. My team-mates similarly moved up by moving out, leading to a rumour mill about a possibly toxic team (it wasn't).

Several years later, my new company merged with the old one, and I ended up under the (new) manager again.

It was time for a change, so yet again I handed in my notice, and she joked that she was "gonna get a complex over this".

So, during the exit interview, I had to make it painstakingly clear that I was absolutely not "quitting the manager" (twice!), just the limited career paths in the company.

That prevented any whispers about the (really sweet) manager being toxic, and reviewing career paths was an example of something the company could (and told me they did) eventually change.