Yes both the United Earth Foreign ministry and the Starfleet Intelligence were not doing their job yet. Perhaps this is why Section 31 had to go into the high gear in the 2150s.
doing their job. The two big existential challenges faced by Earth in that decade came from the Xindi and the Romulans, two species that were not only unknown to the humans but were also mostly unknown to the galactic neighbourhood. (The Vulcans kept knowledge of the Romulans very limited within their own civilization.) They can't be blamed for not knowing that two unknown out-of-area civilizations had it in for Earth.
(It's also not evident that Section 31's meanderings were actually that useful. Wouldn't Trip's original mission have seen him providing support to a Romulan faction that would have been even more anti-Earth than the incumbents?)
As to the peaceful nature of humans. We know that it took till 2130s that United Earth was formed, by the 2070s the people were still barbaric. So I don't see humans defending themselves against 4 fleets (= 4 "wars") in the very early decades of the 22nd century that implausible, after all it would be several generations before the unification is done and humans become such as we see them.
Earth was a Vulcan protectorate during this time period. It's implausible that the Vulcans would have let the Kzin, or any aliens, go after their protectorate. Also, given the nature of the Vulcans' technological lead over the galactic neighbourhood at the time, it's implausible to me that the Kzin would have been more than a nuisance.