The reason the clothing dumps exist is greenwashing. If we weren't pretending that reusing clothing is meaningful to the environment, we'd just burn the clothing locally.
You'd think that cotton could be upcycled - the Soviet Union notably upcycled cotton, by turning it into the duraplast (made of compressed heated old cotton and plastic resin) that made up the body panels of their Trabant cars.
Of course, the Soviet Union doing something doesn't automatically mean it's economical or sensible, but at least in premise it should be useful for something.
Of course, the Soviet Union doing something doesn't automatically mean it's economical or sensible, but at least in premise it should be useful for something.