It is, but isn’t it a pretty standard example of
?
Yes and no. Some of the changes are beneficial, at least for a while. The big one, not so much.
I’m reminded of The Final Countdown – the USS Nimitz is transported to 6 December 1941 and her captain (played by Kirk Douglas) tries to interfere but ultimately isn’t really able to do anything significant.
ST:TNG had that episode where the ship was trapped in a time loop, and the only way to break it was for them to voluntarily scrub the previous day’s events from their history, in order to ensure that everyone on the ship had no memory of the life forms they’d encountered, but Couldn’t Allow Themselves To Remember™. (For the sake of the galaxy or the sanctity of all sentient life or whatever melodrama they attached to it.)
There’s Avengers: Endgame.
That one didn’t turn out better, just less bad.
Bring the Jubilee (Ward Moore) and Times Without Number (John Brunner) both involved time travellers changing history, leading to the world as we know it.
Similar to this is a short story, “Ben Franklin’s Laser”.
A time traveller needs to short-circuit scientific development, so goes back in time to teach Ben Franklin modern electromagnetic theory, which involves (spoiler alert!) building a laser at one point.
…I’ve just started working on a script. And I’ll probably never finish it, and nobody will ever read it, and it will never go into production.
BUT…on the ever-so-tiny chance that it does, then yes, you will have your movie of meddling gone right 
Hmm, it’s raining again.
The protagonist of Lest Darkness Fall was pretty sure that he’d improved the world when he got sent back in time to 5th-century Rome. He invented distillation, the printing press, Arabic numerals, and prevented a devastating war. Amongst other things. There was a sequel written by David Drake where the protagonist is saved by people from the 11th century, whose world had already advanced to time travel science because of the protagonists actions.
In the movie About Time, the main character discovers he, like all males in his family, have the ability to travel back in time to any point in his life. For the most part, going back in time always produced an improvement in his or other people’s lives. The only stipulation is if he travels in time before his children are born, the butterfly effect would cause a different child to be born. Also some events couldn’t be changed in the past because it would prevent him from doing something else that was just as important or more. But usually he could “Groundhog’s Day” himself into a desired outcome.
For the most part, The Terminator films seemingly prevent or delay Judgement Day, which has to be better than the alternative. But mostly they, like a lot of time travel films, create a predestination or bootstrap paradox. For example Kyle Reece going back and becoming John Conner’s father or Marty McFly going back and inspiring Chuck Berry to write Johnny B Goode.
The British TV series The Lazarus Project (TV series) - Wikipedia (not to be confused with a movie of the same name) is excellent. They subvert the butterfly thing, but also kinda not…it’s just an intelligent take on time travel.
The only issue with it is that they’ve only made one series of 8 episodes so far.
In Hot Tub Time Machine three friends send their consciousnesses back in time where they occupy their bodies from 20-30 years ago. One of them, Lou, stays behind, and becomes the cofounder of Lougle. The other 2 when they return find their lives much better due to the new choices they made in the past.
In Timecop Jean Claude Van Damme is a member of an agency that polices time travel and prevents criminals from changing the past - mostly by stealing gold apparently. He uncovers a plot where the Senator who leads the committee that oversees the agency is actually using it to steal money to fund his Presidential campaign. He winds up foiling the plot, killing the Senator, and in the present his dead wife (murdered years ago by the Senator as part of his plan) has come back to life.
How is writing a script different from writing a novel? I have zero experience with the former.
…well, having never written a novel, I can’t exactly say 
But as Darren_Garrison’s link points out, the formatting is standardised. And the reason for that is that the rule of thumb is that about a page of a script is equivalent to a minute of screen time. An example of this is the script for the movie "Shadow in the Cloud, written by Max Landis, used a larger font than normal and when the director “removed the stylistic flourishes” found that there was only enough story for a slightly long Twilight Zone episode.
But I’m still figuring out my own process. I’m starting with the logline (to keep on topic…its something about time-travel!!! Gone right!) then I’ll start planning the rest of it out, from characters, beat sheets, etc, well before I start working on the script. I’ll use Obsidian for the planning stages and outlining, then use Fade In to write the script. I’m not actually expecting to finish, or for the script to be any good But its on my list of things to do, and now is a good a time as any to get started.
Or you could just time-travel into the future, to after it’s been written and polished, and bring it back with you.
I just finished watching “Everything Everywhere All At Once.” In that movie, you get to experience multiple time travel trips all at the same time.
It was by far the weirdest movie I have ever seen, and I have seen “Pink Flamingos”, “Gummo”, and “Eraserhead” in their entireties.
… 
