Unskilled just means pretty much anyone can do it. McDonald's, Walmart cashier, warehouse worker, etc.
You don't need any sort of certification or training. Yes, you need to be "skilled" in that you may need to be physically fit or friendly in social settings, there are definitely plenty of people who are not suited to warehouse work or being a cashier, but if you are suited you can generally start right away with minimal training.
It's still disingenuous to call it unskilled, though. Even those jobs require rudimentary skills that not everyone has. If we diminish the value of these skills, we're just devaluing people even further.
Having to cater to your customers' every need and socializing, keeping eye contact or regulating emotions are necessary skills for a cashier job, yet a mentally disabled person may not have those skills due to their disability. Do you guys just casually forget autism or personality disorders exist?