Thanks for the extra info! I'm really sorry to say this, and this may be naive. Please downvote if you think this is not helpful. But imho:

> [...] or leaving while complaining about different things. All but salary. They had two raises in 2018 and pretty much everyone left got a promotion in 2018.

I'll be honest and guess most people said this probably thought about their compensation. It's not about whether you gave them a promotion, or a raise. If they found a job paying better, with better benefits, they're gonna switch. Now humans aren't robots so you can assume some people will stay in the company for various reasons. But if you see that people systematically leave your company, I think this might mean that you're paying less compared to other tech companies down the street. My 2c. Happy new year!