Seems that checking a box is more critical than keeping some skilled staff. The exit interviews are a joke. Must be checking a box again. New people brought in for specific skill sets are ignored by that status quo. Make sure you write a write paper about something, then you are worshipped, vs, those who actually do something.
HR is a joke, and only there to protect the company, but we all know that. Try reaching out to those who left, find out why. Then follow up. Trust me, others are watching how you handle that.
On a good note, the SE benefits are great. Plenty of perks compared to others. It is a shame the use of people and the skill sets aren't used correctly.