Because half the time, it probably was the situation that made them disappointing? Emberson got waived and was our best D by advanced stats, just a victim of a stacked group. Kostin wasn't getting a chance, now he is and honestly he looked promising. Zetterlund, Granlund (not exactly a prospect...) and Mukh all look like good gets. Whats-his-name from TBL, jury still out.
Yes, it turns out, he's not batting 1.000 because Addison looked really helpful before losing all that, Zadina seemed to struggle, and the other no name prospects in various transactions haven't done much. But overall I don't see the problem, in fact some benefit so far from the strategy.