I would say that in his time he made two genuinely bad signings - 50k on Byrne and 80-100k on Tommy Wright. Asides from that he tried to fill the squad out with short termers, which is exactly what McGhee is trying to do.
Calderwood didn't wreck our youth, it was in a sorry state when he took over and between the management team and our director of football they worked hard to revamp it hence why we have guys like Maguire, Paton and Pawlett coming through and inevitably there will be more next year. Youth systems/academys are not pez machines that just squirt out players as soon as they are up and running, it takes years, look at rangers and the multi million pound set up they have at Murray Park, they have had very little come through since that place came about in comparison to the money spent.