No matter how much they change immigration laws to make it easier to get through the immigration process, it's never enough.
Granting legal status to undocumented immigrants just encourages others to overstay visas, and/or cross the border illegally. Then there is the group designated as childhood arrivals. They are always thought of, and referred to as young children who were brought here by their parents, and didn't have a say in it so there is a lot of sympathy for them. It's often said that this is the only country they know. People forget that many of those children were well into their teens when they arrived here