Why not fix immigration policies instead of making them more extreme?

It is a known fact that almost half of all illegal immigrants come here legally and overstay their legal status.

There are many people who have come here on a work visa and got screwed over by immigration lawyers. Others got screwed by their employers. Other had family or marriage issues. Etc.

While they would like to legally leave USA and come back later with a valid visa, they cannot. Because they would either be detained or banned from entering USA again.

Why is immigration so politicized as a fix all solution to wealth inequality, crime, and poverty, when many of these issues can be fixed with improvements to ridiculous immigration policies