While i am a massive fan of Wallzagli and Marchisio, if you put them instead of Thuram and especially Emerson, it simply means you dont know them.
i'm also a massive fan, thus i'm not objective at all, and i don't expect anyone to be objective either.
still, barzagli is probably the most underrated player i've ever seen (and i'm in my late 30's, i've been following football since the early '80s). i fucking love the guy, he's just as good as anyone in this position (bar prime nesta and cannavaro if you take the last 20 years). i put him on par with thuram, and i prefer barza as he's italian and a more likeable, more loyal character. the same goes for marchisio vs emerson: marchisio is homegrown, loyal as it gets, and also supports attacks better, passes better than emerson (who was a beast defensively, i of course give it to him). i consider marchisio a more versatile player, i think he would fit better in the modern game. i'd pick the prime emerson over him any day if i needed a mid for purely defensive tasks, though.
btw the '16 dybala is at least as good as the '06 del piero. capitano still produced some of his magic after his injury, but his speed faded and he became more predictable.