I don't think the old team was fault free, don't get me wrong: I support Italy, and I would've loved to see Lippi continue, but Lippi's team had its own weaknesses, so let's not put that team on a pedestal (though they already were on one in Berlin). Sure they won the WC but there were some bleak episodes on the way there. (US match, Australia match, Candyman match).
I think that Donadoni wants to build up his own team, but he's afraid (I think) to completely trash Lippi's legacy (and fearing the wrath of a 58 million-head footballing nation), thus he lines up Semioli, Cassano, etc but still calls an off-form Barzagli, etc. It's like he doesn't know where he's standing. IT just like the whole Totti thing. Totti said it he'll come back within a year, so build up a team that doesn't need him, Lippi did it after Totti's injury.
He doesn't know how to handle those problems, definitely a national team, worldcup winner, with all its problems is too much for him. After all his most recent experience if coaching was Livorno, and he quit because of his difference with Aldo Spinelli. When the press start questioning him harshly, I think we'll see that same reaction.