I think the big shift in white sox fortunes was the edge that KW had over other GMs was he had great pro scouting for players that still had something left in the tank and had just been injured or down years.
I think what would be attributed to the increase in Fastball velocity has led to a faster decline of veterans. KW really relied on FA plug-ins and guys being pushed out by new talent. He also took advantage of those "blocked" by vets (CQ, to a much, much lower extent D'angelo Jimenez). I think that wouldn't happen now, as the teams would instead deal the vet and take the younger player.
But, of course it could all just be that hahn was worse at it. There was still players like DJ Lemaheiu nabbed by yanks. There was still players like Zobrist. There was still players like Daniel Murphy with Nats. There was still Nelson Cruz.
Older, 2nd contract players made some big impacts still. Hahn being a ineffectual in drafting and Intl meant he had to hit in FA, and instead he brought us:
Jeff keppinger
Melky Cabrera
Jimmy Rollins
Cody Asche
Edwin Encarnacion
Jon Jay
Adam LaRoche
He bought low on Brett Lawrie, Nomar Mazara, Yonder Alonso,
sorry I have to stop this is too painful.