I thought the game did a pretty good job of showing cops as a gang just like any other in Night City. Of the two cops you work with, one has a questline about the cops being shitty and negligent, and the other is a just fixer who sends you off to do illegal shit like all the other fixers, independent of the police.
Also the cyberpsycho missions were fun, what with the trying to nonlethally arrest super-powered mentally ill criminals to get them help before the NCPD comes in to straight up murder them.
The lack of evidence is just evidence of how totalitarian the Chinese are.