I'd actually say it's the reverse, all labor is unskilled labor, but some of it takes previous unskilled labor to perform and is thus compressed.

The distinction between labor that requires significant existing training and labor that can learn on the job is a useful one. 'Skilled'/'unskilled' is really just a demeaning way of looking at how hard a given laborer would be to replace.

Whether a job must be done by someone one way or another is completely orthogonal. It's depressing how little value people place on the people who do what must be done. Child rearing is probably the archetypical example.