If you don't already know that keeping the name & badge number visible is the most important part of proper policing, and established as such by the world's first police force and its founder, Robert Peel, there's no point arguing much of anything with you.
It's literally the difference between a police force and a Geheime Staat Polizei.
But clearly there are exceptions. You can even read about them on European police websites.
https://handbookgermany.de/en/police
"In particular, criminal police officers also work in "civilian" clothing and therefore are visually unrecognisable as the police force. They often have to hide their identity, for example, to observe people or to enforce arrest warrants."
Dude, WTF
You've never seen a takedown of street level drug dealers? Unmarked cars, plainclothes police, grab everyone off the street?
I'm really trying to understand what specifically you find objectionable. Is it the fact that ICE isn't in uniform? Or that they wear masks? Or that they arrest people?
The moment they make an actual arrest (which is rare, since they prefer to maintain their cover), they identify and are held accountable for how they do it.
Something ICE is not doing.