Oh man, imagine having to watch all of the episodes in chronological order (of the earliest time in the episode), starting with a Q episode, then so many time travel episodes that would make no sense, then... Enterprise, Some of disco, and strange new worlds, then tos, with more mixed in, etc.
My headcanon is after the events of "The City on the Edge of Forever", everyone agrees that maybe fucking around with time travel is a bad idea after all and they just avoid the whole thing (except for that one time with that alien and his sentient cat. No, not that one, the other one).