I can’t speak for them, but in Chicago the police never got into mask enforcement. None of the law enforcement agencies were too thrilled about being called upon to use the criminal laws to address a public health crisis.
Some of the regulatory agencies did monitor restaurants and bars the best they could, but it wasn’t nearly enough so most places slipped through the cracks.
The fact is that most people, vaccinated or not, will obey a sign on a door stating the mask policy. (Although this may no longer be true if vaccinated people believe the CDC and reject the idea that they are spreading the virus.) The police just don’t have the resources or will to go after citizens for not wearing masks.