Cassano had a fight with his son, do you expect him to pick him? Not to mention the indiscipline in all of Cassano's career (I don't buy the bullshit that he changed). Italy won the World Cup without Cassano, in the Euros, in the group deciding game against France, Cassano had already booked a private jet to take him home after the match. That is how bad his attitude is.
There were differences between Miccoli and Mr. Lippi since Fabrizio was at Juventus. You can't blame a coach for not picking players he has arguments with, it's like someone blaming the boss for firing a person who pissed him off. There has to be at least a working relationship.
Gattuso was good for team spirit, he is a very important factor in the dressing room. The things I blame the Mister for are using Gilardino while everyone knows he flops in the big games/big stages, not starting Di Natale who was Serie A's top scorer (29 goals) and a creative force upfront, and trusting Cannavaro instead of grooming a young defender to take his place since he took charge.
A lot of factors went against Mr. Lippi like Pirlo's injury, and Buffon's injury. But yes the team was very bad, but it's not always right to blast the coach without any means of understanding.