This piece is two distinct and good articles, but they don't actually fit together into one whole for me. The first part is about how some kids of divorced families grow up internalizing the values of the parent who is not providing standards and boundaries for healthy maturity. The second part is about getting the stereotypical "basement-dwelling" adult child to move on. Both parts are good but you're not actually talking about the same kid here.

The adult child of divorce can just move to the other parent's home, or be financed through life by the other parent (and their supporters), or comply grudgingly, while continuing to believe the narrative of the other parent, distorting their natural state of love and loyalty to both parents. You cannot parent a child in the same way after divorce that you would if both parents were on board, no matter how old they are. Parents need time to practice "not backing down" about many small things before they can bust out the big guns and actually follow through to kick an adult child out of their home with the confidence that this will lead to love and respect down the road. This is the part they skipped over when they were sidetracked by the "crashing chaos" caused by the divorce conflict and their own fear of incurring the wrath of the other parent. Doing what you say you're going to do has to be the constant refrain of all your interactions with your child - you have to learn how to give that lesson consistently first before you can expect your child to learn it from you.