Virtually all corporate ghouls support open borders. Almost every single elite supports open borders. The fact that the Democrats refuse say anything here is outrageous.
Dems should absolutely attack Trump for not following through on his promised mass deportations, but only because they are not actually happening.
Mass deportations are one of those things that are popular only when they are not happening. It sounds to a lot of low info voter types as though it would be good, because they don't think far enough ahead to realize that would entail other consequences (in particular, the previously mentioned spike in food prices).
However, I don't think that applies to you, you are not a low info voter and you obviously do think things through enough to post here.
So, let's try to think this through.
If Trump changes course and actually does begin mass deportations, then it will play out similarly to the tariffs, with it starting to become unpopular as soon as it starts to have real tangible real world economic collateral damage. Suddenly there would be nobody to pick crops from the fields, nobody to milk the cows, and nobody to chop up the meat in the meat packing plants.
Now, I assume what you are thinking is that would be a good thing, with the idea that it would raise wages. And in the short term, I do agree with you that at least to some degree it would.
However, it would primarily raise nominal wages in the sectors/jobs most affected which currently use the most immigrant labor. And by definition, those are the sectors/jobs that are least attractive to American workers currently. So for example, meat packing plants would have to raise wages in order to desperately try to persuade more American workers to work there. But nominal wages wouldn't rise - or wouldn't rise much in comparison - in the other sectors/jobs in which American workers are currently working. And for the American workers in those other sectors, real wages would drop, because they would all be paying a lot more for food and other things that were previously produced using immigrant labor.
Moreover, in the mid-to-long term, what would happen is that this would greatly increase the economic pressure for industries/jobs which previously had employed immigrant labor to innovate with the introduction of new labor-saving technology in order to reduce their skyrocketing labor costs. More research and development would be devoted to things like crop-picking-robots, and meat-packing robots, and because of the greater effort/focus on that sort of thing, breakthroughs would start to be made and robots that previously would have been uneconomical (because immigrant labor was cheaper) would become economical, and would start to displace the American labor that you want.
And then when this new labor-saving technology were introduced, that would reduce the pressure for higher nominal wages that the mass deportations achieved in the first place, so any of the wage gains for American workers you were hoping to get as a result of the mass deportations could prove to be just transitory blips.
So I don't think that this is really the great solution to making things better for American workers that you might think it is.