The point here is that theoretical economic analysis presumes labor surplus. Academically trained economists do not, at the most basic level, understand or know how to reason about an economy that is not in labor surplus: it simply baffles them. The only policy recommendations that they can formulate reduce to "first create a labor surplus so that we can apply the formulas that we were taught."
Job openings don't stay open because there's a labor shortage, they stay open because the employer isn't offering competitive compensation.
Yup. In a free market, there are no shortages.
We just have a glut of employers who do not want to pay market wages.