It's a general criticism of the system. Highlighting Amazon's particular behaviour is useful as a demonstration of how/where the system fails, and may produce short term wins if it incentivises amazon to stop being inhumane.
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.
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.