Travis Shaw was not really a prospect when traded, but he put up a couple season's of good numbers, and we got squat, but your point is a good one.
Kopech, Margot and Moncada have been okay, when healthy, but none look to be as good as Devers, Bello and Casas. Hell, Duran and Rafaela may end up better than each of these guys.
Espinal is the unsung one that got away (5.2 bWAR.)
Beeks looked like he might be good, but not so much, anymore.
Hell, as little as Bloom has traded away, Springs might be better than anyone DD traded.