In-universe there may not be anything more remarkable about Kirk's 5 year mission than whatever Pike goes through in SNW. Yet repeatedly Kirk's tenure is defined as historic in-universe. It's only because his 5 year mission had a tv show in real life. Otherwise, compared to what Pike is doing now it's probably nothing remarkable. Most of Kirk's Federation shattering actions happen in the TOS movies, mainly saving Earth from V'Ger and the Whale probe. Pike saved the universe from Control, and the only reason no one knows about it is because it was classified.