First a bit of context. In Germany, some companies have something called a works council. A body of employees that represents the interests of the workforce vis-à-vis the employer.
The works council has certain rights and is well protected against reprisals. And it is bound to confidentiality.
For works councils, exit interviews are a valuable way to learn about problems that have previously flown under the radar. And in most cases, the works council is interested in improving things.
In many cases, it has the means to do so. It may take some time, as everything does, but in my experience exit interviews can help.