If players slide underneath after the offensive player has left the floor, then it is not a charge.
What your saying defeats the entire ideology behind defending anywhere on the floor. As a defender your goal is to get and stay infront of the offensive player. Are you saying the only way you should be allowed to defend the basket is to try to block a shot from the side?
Players will just try to play defense on the ball. Help defenses will help by getting over and making a play on the ball instead of sliding underneath a player in flight and causing a pile up of bodies on the floor.
That's a block. I really hope you've never called it a charge.
Full disclosure: I reffed HS, college club, and juco for years. I now coach.