Perhaps you were a bit curious to see Zambrotta and Thuram, too? Of course they were not in their prime then (as Buffon wasn't neither), but I believe it was the right decision to let Valdes play, I believe he did better than Buffon would've. Both faster off his line, better with the ball, and probably stronger 1v1.
Zambrotta was actually very good for us, especially on left side at which he was natural there. But at 30 we expected him to be the best FB in the world which was unfair back then. His wife wanted to go back to Italy and we saw an opportunity with Alves so we moved on smoothly, it was a win for everyone involved. But in no way Zambrotta was kicked out or was bad for us.
Thuram was 34 going 35, he was a bit undersized and lost his athletic ability, it was a bad deal.
At 34+ even the likes of Puyol, Pique, Mascherano were either gone or were as bad, when they were at the same age of Thuram when he joined us.
Buffon was 28, his peak ended after Valdes was done as a professional GK.
And Valdes wasn't a ball playing GK until Pep came and forced him to be, telling him he can live with his mistakes (and god, there was plenty) as long as he stick to it. We don't know how Buffon would have done in such circumstances and whether he would have adapted or not. It will always remain theoretical argument.
The reason we didn't go for Buffon was because he didn't push for it, so Juve were in a position to ask for a record fee for a GK that we weren't willing to pay, especially when we knew that Valdes can do the job and had his best game in CL.
The passing thing was more if a later execuse.