Unfortunately no. You can't teach the unwilling. As hard as that is - unfortunately that is the truth. I can teach a class for hours and hours and hours - if someone is unwilling - there will never be any change. It's these people that end up with a dog that they don't know how to control. Don't know how to train. Wonder why their dog is so bad, tell everyone that their dog can't be trained, and that no trainer will be able to work with their dog.
The fact that you can spend a bit of time with their pup and train it some simple commands should be enough proof for them that it's possible if they put a bit of time in, they can have a great dog. But they have to be willing...bottom line. A lot of people aren't willing. They don't make the same commitment that most of the people on this board make. A lifetime of love, care, affection, training, lessons, learning etc. etc. etc. A lot of people assume that a dog is just supposed to get better as they grow up. A lot of people think it's normal for a dog to be destructive. A lot of people think it's normal for a dog to have no manners. Honestly I could go on and on and on.
BOTTOM LINE - it's not your fault and you can't beat yourself up about it. I know that ultimately the dog will suffer. It's these kind of people that end up with a crazy dog and then months, sometimes years later decide to get rid of the dog. It is a huge problem that unfortunately we can't do much about.