Penalties are a lottery win. All about choosing your luck and beating the keeper. The ref didn't do much right, I agree. We definitely had the upper hand on the game but testing the Chelsea Manager in goal wasn't frequent enough and VAR caught Sergio's bottom offside.
They aren't though. The same thing was said about England losing them all the time and Germany winning them. They aren't a lottery, they are the application of technique under pressure. City practise them, and practise them frequently, and as a result they're very good at them. This isn't luck, and it isn't a lottery. It is preparation.