If the workers want better conditions they can leave.
If all options are below what we would consider moral then we should change laws. The solution to a problem in a free market is not inside of one company.
It sounds like you assume that corporations are immutable things, whose contracts and policies may never be changed. But we are having this conversation because Amazon’s policies changed, and the workers it affects are complaining. Why isn’t “Amazon rescinds this policy change” a solution to this problem?
Other truckers have UNIONS. Their cockpit recorders can only be accessed under strict guidance and policy - not willy nilly to piss off the truckers. Plus they get reasonable quotas so they don't have to bust their asses and drive sleep deprived.
> the solution in a free market...
... is to create a fair labor market. The labor market is not a free market, because companies have infinitely more leverage. If you're truly a free market activist, you must be pro-union. Introduce a little competitiveness into hiring practices.