So what you're saying is...it's capitalism's fault?
It is Ok to say that unrestrained capitalism is at fault, because that has led to this. Or capitalism that hasn't adjusted for the modern standards, perhaps.
Abuse is what is happening now, and the proper solution is laws to hinder such things. If it were up to me, a lot more places would be a socialist democracy with a thriving capitalistic sector.
Any concessions to this only come from fear that the bourgeoisie would lose further power, which explains why the rich historically supported the expansion of the middle class as it created a buffer between their interests and the interests of laborers, and would explain why Jeff Bezos would support a living wage now as without it there is an increased risk of having to make further concessions down the line.
I'm not sure, but I think most places are OK with bathroom breaks. I could be wrong, though.
If so, why didn't the employees change jobs? See, this is much more difficult. If the Amazon warehouse pays more than other jobs around - even if the pay is still low - it makes it much more difficult to leave the job. You still need food and electricity and so on. The same sort of thing happens if an employer pays less, yet offers things like decent, affordable health insurance (or health insurance at all). To leave a job simply because of working conditions is a position with a bit of leeway.
If not, why is so much criticism directed at Amazon specifically, rather than at capitalism itself?
It isn't directed only at Amazon, but large employers. I'm not sure why some of the anger isn't directed elsewhere, though. I'm not sure it is fully capitalism's fault, but more of lack of laws protecting folks from capitalism alongside adequate enforcement of those laws. It is easier, however, to direct anger at the company, who can change somewhat rapidly, rather than a government that is slow to act and rarely produces quality change for all.