There are certainly some lobbies that don't have cheaters in it, and most of the ones that I had played in normally always had some cheater rotate in after a prolonged duration. Not sure how it has been recently since I haven't played much recently, I normally lurk the official forums / subreddit, keeping my eye out on any new announcement about what they are doing with cheating in GTA:O. Wished they had picked up VAC or somethin', just to get them removed far more swiftly.
It's definitely a buzz kill experience when one pops out of the shadows with god mod on, spitting out rockets of his assault rifle.