It’s tough to improve in college, honestly.
Devon is exceptionally quick, so when he comes off screens at the college level, if he’s even with a guy, the right play is to continue to the basket for a layup. That’s just the right play. So even though he needs to work on his jumper, because he can beat guys off the dribble with such ease at the college level, the right play is the layup. That doesn’t help him improve his jumper.
And that’s the thing with potential NBA guys. The things they do best are more than enough to dominate at the college level. Devon is working on making the correct read, and the correct read more often than not in college will be to continue his drive because he has his man beat on that screen.
The NBA doesn’t so much care about college hoops because the guys they are targeting are already better than the collegiate competition. That’s why the G-League has started gaining so much momentum. Teams need a better evaluation tool than the college game offers. Look at the schedule KU has had this season so far. There are maybe four games out of eleven that are worth evaluating as an NBA scout - Duke, Dayton, Colorado, and Villanova. The rest of those games are basically worthless for evaluation purposes at the pro level.
@DoubleDD is right. It’s just a different game. Higher talent level. More complex schemes. More demanding overall.