Part of a GM's job is to assess who's overvalued/undervalued, not just rely on journalist rankings. Not only did Rizzo get ripped off, he tried to cover his butt by giving Keibert that ridiculous contract extension.
I agree that trade is underwhelming in hindsight. I've just seen a lot of people act like Ruiz and Gray weren't considered top 100 prospects at the time of the trade (not that that is what zimm_da_kid was saying).