Imagine someone mortgaged their house to invest with Bernie Madoff.
Then they lost it all when his scheme collapsed.
And people insisted the taxpayers should pay off that mortgage for him, and let Bernie keep all the money he stole.
Student loan forgiveness is like that.
If someone should be on the hook for swindling kids out of hundreds of thousands of dollars for worthless degrees, it should be the institutions that charged them and provided the degrees.
IMO even that's too far.
There is nothing illegal about selling "useless" knowledge. If you wanted me to teach you about a topic, and I offered to do so for X dollars, that's up to you if you think it's worth that or not. My side of the equation is following through on providing appropriate instruction which allows you to learn said topic provided you do the assignments and study. It's up to you what you do with that knowledge afterwards.