1st point in regards to Buffon. All the more reason to sell him now, while he still has several good years left in him. His value isn't going to be any higher if they wait another year or two.
In regards to your other points as far as filling in the holes, I don't think that Juve had much of a choice but to overpay for players that most teams would have paid 2/3rds of the price for, because of the expectations with this team from its fans, and their own vision of what Juve should be.
That was a dangerous game to play, and the results clearly show, with a few exceptions, that they lost.
Which is all the more reason to blow it all up and start all over again. I'm totally cool with that, not that my opinion matters to anyone in Turin.