I don't think it's fair to say Giddens was a "mediocre prospect." He was originally projected to be a Top 20 pick, for crying out loud! He slipped his sophomore year, yes, because people questioned his devotion to the team; however, coming to the Celtics he would be playing with Leon Powe and Kendrick Perkins, who he was friends with (and had played with at the 2003 McDonald's All-American Game), so there was good reason to think he might click in Boston.
It didn't work out, yes, but hindsight is 20/20. Seriously, Jordan was not a consensus pick at the time (heck, if you look back at a bunch of articles from the time, most commentators don't even mention his name as a Boston prospect). Everyone in the whole [dang]ed league missed out on him, that's why he was drafted in the 2nd round. Get over it.