He’s not ruining anything, you are reacting as if he can change. That creates conflict in the house. He must find a discipline. Give him nothing more and toss him out on his butt until he does. If you won’t do this because of __________________ (fill in excuse here) you are simply enabling him. This is not a judgment of your parenting, it is just basic human behavior.
A discipline is simply an interest that triggers a dopamine response that drives self-motivation. It doesn’t have to make money today, but it should when he is skilled.
NOTE: He will not do anything as long as you coddle him. Ever. Then when you die he is screwed.