I said this on the other thread, but here goes: Spock doesn't have the right
to undo 25 years of everyone's lives. It would effectively be the murder of Kirk and co, replacing them with their TOS versions.
Even if he somehow went back and stopped the Nerada in 2233 (which they barely
managed in 2258, and another attempt could lead to utter disaster), he may save Vulcan, but at the expense of Romulus and Remus who are fated to die a firey death in the original timeline. With the foreknowledge of events the STXI people have, those deaths (which likely exceed the six billion Vulcans) may well be avoided in alternate 2387.
Would Vulcans want their world saved at the expense of two
others? Even those of their enemies? I think not.