It absolutely does not need to go away. And no, him developing a midrange shot would not help his value, it would hurt it. Teams would pray Duren shoots the midrange all game.
League averages by distance:
At rim: 65–70%
Midrange: 40–45%
Three-point: 35–38%
What that translates to as points per shot
Rim: 0.68 × 2 = 1.36 points
Midrange: 0.43 × 2 = 0.86 points
Three: 0.36 × 3 = 1.08 points
If you’re shooting 43% from 18 feet, that’s equivalent to shooting about 29% from three. Congrats, way to spend all of those developmental hours on turning Duren into Ausar Thompson.
Get him in a gym this summer shooting thousands of three's. He doesn't have be Steph here, he doesn't have to shoot 40%. 33% is the floor, if he can hit that then defenses at least have to pay attention to him out there. That would create a lot of spacing for Cade and others, unlike Duren shooting the midrange where his defender will still be near the paint.