Being a long-time night-shifter I will try not to get my defenses up. I have worked too many places where people from other shifts make all kinds of assumptions--until they have to work a night shift. Then they see the reality that nights has plenty to do. Part of the problem is that much of what night's does is invisible--until it isn't done. It's difficult to give due appreciation for things that only show up by omission. At any rate, every place I have ever worked, the night staff took their jobs seriously.
That said, I have heard plenty of horror stories from people whose word I trust. What you are describing is a problem involving both substandard individuals and poor management. Night shift is an easier shift to abuse, and you can run into a situation where various people have cut deals allowing each other to pull all kinds of shenanigans. No one says anything because pretty much everyone has something to hide. This system continues until someone new shows up, someone who won't play the "go along to get along" game. Then they are either harrassed and intimidated until they quit, or they finally squawk long enough and loud enough for management to take matters seriously.
If the powers that be are serious about running a decent facility, they need to start showing up at random times during the night to make certain that staff are awake and performing their duties. They need to find out if the last round is the only round or if residents are truly being turned and changed throughout the shift. They need to stop looking the other way just so they can say they have proper staffing on paper. And they need to start canning staff members who are lazy, who have attitude, and who have become overconfident that their jobs are safe no matter what kind of garbage they pull. If management can identify the pack leaders and get rid of them, the more malleable staff members can probably be reshaped into decent employees, but that won't happen unless the real troublemakers are booted.
All you can really do is report what you see. Document for your own benefit. Names, times, dates, tasks that were not done, excuses made, improper behavior caught (sleeping, watching TV, playing cards, etc.). If management takes no action when presented with this information, you will know to look for employment someplace else.
If your complaints are not taken seriously, you can also place anonymous calls to JCAHO, your state organization that governs LTC facilities, media outlets, and anyone else you can think of.
I wish you well.