Screen Time limits an hoax?

We have been trying for years to use the screen time limits correctly for our kids…. Whatever we do they can go around them and still play games and watch series…. Never the option to have the app stopped at the end of the limit worked…. and the kids do not have any password…. Exemple, 15mn daily limits on Instagram and our son spend 16h in a week on the App…. Anyone got it right? Thanks 🙏🏻