Sure the issue is when employees don't feel like they can leave, because they can't afford a period of unemployment and don't have the time/energy to seek new employment whilst working 12 hour shifts and potentially supporting a family.
Is your issue with Amazon, or with the system of capitalism in general? If the latter, why are people criticizing Amazon specifically?
You get a more functional labour economy by having labour able to access better opportunities. If there's a killer sales agent that won't apply for my sales position because Amazon is dunking him with 14 hour days repeatedly, no one benefits besides Amazon.
To answer from another perspective, a society resembling something like socialism or anarchism is what I personally would prefer to live in. I have doubts about whether we can move towards that from the current situation or whether it's workable, full stop. But it sure would be nice.