996: 9 a.m. to 9 p.m., 6 days a week
Sure, they're burnt out, sluggish, surly, but... they're present. And when they're present, they're not out in the world spending their income. They don't need an expensive apartment or house, all they do there is sleep. Why have a fancy car when all you do is drive to/from your shitty job in it? Family? Who would have children with somebody who works such a schedule?
Even if you got more productivity from the same workers on a 9 a.m. to 3 p.m., 4 days a week schedule, you'd have to pay them more, not just per hour but overall, because they'd be out spending money on those afternoons / evenings and 3 days a week they have off. Organizing, demanding better healthcare, dental, more paid time off for vacations, and higher total wages to support all these "needs" they invent for themselves on their time off.
Keep 'em locked down, keep 'em tasked with ... anything, doesn't matter if it's productive or not, as long as it keeps them on-the-job and not spending their pay.
Edit: apparently this isn't clear: 996 is a horrible idea from all perspectives, it's bad for the workers and bad for their employers overall. But, in certain twisted views, it would be a bit like military service where the (bulk of the) workers get a pitifully small paycheck, but they don't have any real expenses so they have the option to save it all. 996 would turn that more into a wage-slave implementation where the pitifully small paycheck is just enough to meet their pitifully small expenses. In the China tech sector where they have implemented this (it is now illegal, but still practiced) they also do things like install anti-suicide nets in the stairwells of the highrises the workers work and sleep in.
Well, really, it's wage slavery. Work is all you have, and the pay you get is not enough to give you any freedom from the work.
As you say, you don't have enough time / energy to go look for another job - such places also intimidate the workforce and arbitrarily fire workers who might signal that they are looking for another job (such firing probably being a favor in the long run, but not if you starve to death in the meantime...)
Ben & Jerry had it right with a 5:1 ratio. No person in a company's time is "worth" more than 5x the value of another person's time. Some incentive to develop skills, advance in your role, recognition of better performance, sure. At 5x, that should be enough to recognize your investment in yourself and your skills and your commitment to the company vs some guy who just shows up to push a broom. It wasn't so out of line with "reality" when they did it in the 1980s, but today it just doesn't work - the US is stratifying into classes/castes like the ones India is trying to abolish, just without explicit labels. The US system is based on how many digits are in your annual income figure: 4, 5, 6, 7, more?
UBI would go a long way toward rectifying all of this. Let business do what they will, provide every citizen with enough money to live, instead of 0 + whatever they can squeeze out of the bureacrazy by "demonstrating need." If "illegals" can earn enough to live better here than elsewhere without any UBI, let them - if they get into financial trouble, give them assistance getting back to where they came from - otherwise: live and let live. At the very least, businesses would have to improve working conditions - otherwise the workers would just stay home until they find a better deal elsewhere. I can tell you from experience in the disabled community: people want work, they want to get out and have their value to society acknowledged with a paycheck - they also like to be able to buy shiny things. The current welfare system is a big bureaucratic stick hanging over their head threatening to beat them with benefit cancellation if they do get out and earn a little money.