Playing the devil's advocate for a moment here, but would the point of "unskilled" labour not be work that is replaceable in near future by robots? Generally the whole schtick has played on having or not having the shiny college degree paper, and it is true that constructing a blueprint for a building structure takes more skill than cleaning a sewer, EVEN IF both are extremely hard jobs to do. One has consequences like death for hundreds or thousands of people.
The pay wage divide created by bourgeois class seems to be another plane of this multi dimensional problem.