I never stated Del Piero was useless, but if I had to choose between selling Diego to start DP, and benching DP and keeping Diego, I would choose the latter option 100 times out of 100 for the current Juve.
We did buy a few players who have been an absolute waste of money and space, such as Grosso and Tiago. As for Giovinco, he was not sold, merely went to Parma on a co-ownership, so there is hope for him yet. This is a make or break season for him; should he prove himself at Parma, he is more than welcome to come back and fight for a starting shirt @ Juve.