I have to agree with the OP. There is no setting i have not tried with team and individual instruction that works to get the team to defend against AI. One through ball and the defense does nothing to stop the ball, not in terms of heading the ball away or trying to catch the run away AI striker. Its as if they suddenly develop lead in their boots and don't bother to mark. Same with wing backs / full backs. They are always allowing the opposition wingers to use them as scape goats. There is no marking from them either and leave so much space for the AI to play with. Every year the problems keep growing bigger and bigger with each release of the game. I am seriously losing faith in Football Manager and it will take a HUGE SWORD OF DAMOCLES to land on my head before i part with my money to purchase FM 2021.