How is a “labor shortage” a bad thing? You can ask for more pay if there’s not many people who could do the job.

In other words, birthright citizenship exists to increase the population size.

Birthright citizenship is a law made at a time when the American population was significantly smaller and wanted to grow to be able to provide more workforce to bring about progress, which benefitted everyone. Now, progress is ending/slowing down, and demand for human labor is declining; and a shrinking population is a good thing because it matches that shrinking demand for labor. Immigration is a bad thing because it increases the population size instead of decreasing it. And also, the birthrate should drop lower to reduce the supply of workforce, keep up wages (via supply-demand of labor) and better the living conditions of the people.