My own experience is that you either have soft hands or you don't.
If you get to this level, done this much work, you probably have the hands you have.
When you are in HS your coach might have you tossing eggs or bricks to learn how to catch (I doubt they let you toss bricks anymore, but who knows).
There can be some changeover with drops like happened to that kid playing on the Bengals, who looks decent now but looked terrible in preseason because he was getting used to the ball. But it feels like a bit of a pipedream to expect DK to just get better hands, even with tons of time with the JUGS machine.
DK is going to drop balls. You have to expect that sometimes that it will be a homerun or sometimes a drop. It seems to be primarily in traffic, he hasn't dropped that many open shots. So it MIGHT be a concentration issue (which is fixable) or it might be that his hands are easy to disrupt by the defender.
I don't like all these sideline patterns AT ALL.
Would also like to see passes to him without him standing still, since he take a bit to get up to speed. The short passes are fine with some momentum, but for some reason we love to throw to him with blockers in front of him but no momentum at all.
But to expect that DK will just become a reliable target is asking a bit much. He has a ton of physical gifts, we need to give him more chances to catch the ball while moving that are not just low % long balls. But we need to accept that he isn't going to catch everything thrown to him, and be able to work with it.