The chaos principle at work.
Invariably followed by the strawman "we can't deport them all", therefor we need "reform".
Incentivizing criminal behavior while thwarting law enforcement are tactics. The left is holding the country hostage until their demands are met. They seek a constituency accustomed to strong-man governments and public dole, a constituency refusing to be acculturated with American values, one instead clinging to their culture and language.
I agree with what you said except the part about “cant deport them all” being a straw argument. It is a legit argument, but the difference is in what you do once you realize this.
The left, as you said, uses it as a cop out to accept all of their utopian dream programs. A conservative would look at this fact and say, okay, let’s do what we can to make this happen over time. Seal the border, remove the hand out incentives, deport those in custody and convicted of crimes, and then watch supply, demand, and human nature self correct a problem that was caused by human nature, supply and demand, and bad policies regarding the border and hand outs,