Well, disregarding the spin-offs, TOS did time travel what, 5 times? Out of 79 episodes, it was done 5 times. And it was always done well. So, number one, it hasn't been "Done to death". Not where it counts anyway.
Add to that the fact that the most successful Trek movie of all time was Trek 4: The Voyage Home. Making a TOS movie with a plot revolving around time travel makes perfect sense.
Add to that the fact that the most successful Trek movie of all time was Trek 4: The Voyage Home. Making a TOS movie with a plot revolving around time travel makes perfect sense.