It wasn't good at that factory, to be sure. I'd estimate that engineers were costing the company money on balance for the first year and a half of their employment -- there was a lot to learn about the process, how the factory ran, working with other departments, and so forth. Bad engineering decisions were very expensive. So when you have a pool of engineers who are mostly too inexperienced to make good decisions, a lot of bad decisions get made. Given the attrition rate, about 50% of engineers were running around making bad decisions, or no decisions at all, at any given time.

That feels (to me) about normal for engineering though; I feel like a lot of engineers tend to stay for around 2-3 years; roughly, ~40% percent per year turnover?

Not that this is necessarily a good thing. I feel like most of the turnover is completely preventable, should the employer want to actually keep employees for longer than 2-3 years…