thank you for your commenting all. But now I realized that "this kind of Perfect Government" and "less human behavior is actually possible in the world of Trek. But don't think that I will give the credit to human. No, humanity changed not because they realized their mistake after WWIII. The reason is too naive.
I think, the most logical reason is that because they are being exposed to many Alien cultures. Look at us, we love to copy other people behavior. So, what prevent us to mimicking Vulcan?
Come on, who can resist Vulcan? Look at them. Even with nerd hair cut and naive eyes, Vulcan is actually a bad ass. They can kick their enemy around with only touch their shoulder. And they clever like hell. No human children could win a science competition against Vulcan. That's why Vulcan can become the role model of some people.
And because they interact closely for more than three centuries, it is possible that some human has become more "Vulcan" than their ancestor. I think, it is the most possible answer for this problem.
Why human is so weak and easily to exposed by more advanced cultural entity? We have some examples in real life. Look at Japanese. They are more American than their ancestor now. And not only them, there are a lot of cultural transfer and change of behaviors in our world. Some because of culture, other because of religion. That's why the human in 24th century is also exposed and maybe influenced by the foreign culture, like Vulcan, or Klingon, or Romulan, or the others. It is a natural way of life in our universe.
Just curious is English your primary language?
I wouldn't give Vulcan's that much credit, sure they open our eyes, but even in ST:ENT, they clearly stated humanity changed itself after "First Contact" happened.
Vulcan's were a inspiration as to what is capable for a civiliation / species potential.
However, the change happened because humanity was determined to improve so they can move on past all the old problems and deal with new issues regarding space exploration and the possibility of spreading human kind into the stars.
All Human's on Earth would have learned that it needed to not place it's species all on 1 planet after WW3, ergo fixing basic problems and readying themselves for colonization would be a huge priority for the human race.
I said that I'm Asian, isn't it? so English is basically not my primary language.
I doubt that the reason is like that. It's too idealistic. Almost impossible to be realized. Exposed or influenced by the outside worlds is more "logical" and do-able. If you are Asian, then you should know that some of Asian countries are influenced by other culture. You can see at some of Islamic Countries like Indonesia. They are more Arabian than Indonesian, just because they are influenced by the religion. It is also happen to Japan. Look at them before the Meiji Restoration and then look the different after they take western culture.