Some of the same points op made in the other thread. It wasn't that we lacked the athleticism or quickness to guard them.
Lots of help mistakes and lots of pick and roll mistakes.
I'll take this chance to ask op a question since he's obviously something of an expert:
In guarding the pick and roll it seems to me that, unless the dribbler is not a shooting threat or the big is hedging, the other two options would be switching and fighting over the top. Except for the two options I cited, I just don't see going under the screen ever being the correct option. Am I wrong? (if I am don't worry; I can take being told I'm wrong)