The main place where ICE has removed oversight has been when they have detained people; they don't document clearly whether the detention was for immigration or suspected immigration offenses or more general obstruction offenses. After the fact, they split these claims, saying that all detentions not resulting in immigration enforcement were just "obstruction" all along. So we have no idea how often they are detaining people because they think that they are illegal, but, on finding out that they are legally present or citizens, claim that it was obstruction all along.
I think we're in agreement here that the administration has pushed to limit accountability and auditing, and ICE and ERO and DHS and Border Control have all been using this to make themselves look like they are much more well-intentioned than they likely are. Where we differ is that you think they are successful at this, that they are portrayed as competent and earnest despite the reality. Whereas I see that they have been vilified to an almost insane degree in almost every media outlet that I have exposure to.
But the thing that they can't lie about, that they can't cover up, is deportations, because these are big news and everyone knows it, and false and improper deportations are a huge deal and have been every time they have surfaced. That you think there are more cases that have not been chased down by lawyers hungering for a lawsuit and NGOs champing at the bit to try to bring these people forward is disconnected from reality to a degree that I can't comprehend.