I'm really surprised that DL lets you see on the app whether the bag had made your flight. I would imagine that this could lead to some upset passengers on board.

Still, I agree that that "wait and see and then report the bag as missing after wasting time waiting for it to appear" system has never made sense. In small airports when only a few bags aren't going to arrive, passengers could be paged to the baggage office. More generally, the information could appear on monitors near the belt for the flight, with a list of either names, seats, or tag numbers of those known to have missing bags, although there could be ambiguity if the passenger has checked multiple bags.