Pretty strong evidence that the job is worse than people would expect would be an anonymous survey of workers by a third party.
Churn can result from any number of factors. It simply isn't enough to support your conclusion, and a lack of imagination in seeing alternative explanations isn't proof. Warehouse jobs have high churn. Yes, Amazon's churn is higher.
A pandemic is just ending. Amazon hired a lot of temporary staff. Temporary staff are temporary.
As things open people have more employment options. People will always go to the best option available. That doesn't mean the job they left is inhumane. It means they found something better.
Finally, Amazon has a signing bonus. Some workers may be there just for the bonus. Once they get it they may want something that pays less but is easier.
Do we know which positions are leaving? Is it the back breaking jobs, or the higher level stuff? I don't imagine any the back breaking portion would ever be "good". It's seems like fast food, something that should be transitory, where you move on to better things (even if that's fast food management). Physical labor is a young persons job, because bodies break. It's not something you could stay with if you wanted to.
If it's the skilled positions, like mechanics, engineers, forklift operators, operations, etc, that are leaving, then I think that would be better evidence. If it's the guys moving boxes, maybe not.
Even for tech jobs, where it's common to interview with many future coworkers, assessing the work environment is tough. Warehouse type jobs are probably even harder to evaluate.