They enforce the law where they should which is why deportations were higher under Biden than under Trump.Except for the millions of times that it hasn't. Perhaps as many as 30 million times?
Besides, there are quite a few prominent Democrats who disagree with you, because they have vowed not to co-operate with, or even to oppose, ICE deportation actions.
Sanctuary cities issue ordinances choosing to protect undocumented immigrants, so it does not fall under lack of enforcement.
Lack of enforcement, is willful negligence.
That does not happen.