The idea of time travel is seductive. Who doesn’t agonize over that one thing they said that blew their chances with that one girl that one time and how if they could have changed it their life would have been awesome? So time travel shows up in movies. A lot.
Let’s ignore the mechanics of time travel for a minute. Whether an alternate universe is created by going back in time (Star Trek) or it’s part of the same continuity that can be changed (Back to the Future) or it’s part of the same continuity that can’t be changed (implied in Harry Potter and the Prisoner of Azkaban)
But no matter the mechanics* there is a universal feature of time travel that can ruin the movie: time travel literally solves every problem in a completely stress-free way.
*The one movie with acceptable time travel mechanics is “Primer”, a movie which will definitely get its own post soon.
Without a time deadline, there is no pressure. When was the last time your boss or teacher said, “Yeah, just get it done whenever” and you actually cared about getting it done? This is what it’s like in all time travel movies. In “Azkaban” the protagonists travel back in time and are rushing to save Harry’s uncle. But…what’s the rush? If they’re late, they just go back in time again! They are quite literally in a position in which they cannot fail. Not bad.
But, wait, it gets worse. Remember in the fifth book when Sirius dies? He dies because Harry misinterpreted telepathic signals from Voldemort and his allies were ambushed. So…I’d say it’s time someone went back in time to stop the ambush…right? Time travel clearly isn’t a one-time thing; Hermione had been using it to take a double-load the entire school year. So, every time an ally is killed, they should be able to go back in time and prevent it. That they don’t either means the characters decided that letting a 14 year old get to class on time is the only thing important enough to justify time travel or J.K Rowling realized after the third book that time travel is too powerful a mechanic to have. The latter? Yeah, I think it was the latter.
The entire Star Trek franchise also has a problem with this. It’s established multiple times with the original cast that if you slingshot around a gravity well (like a star) you can go back and forth through time. That’s not actually how relativity works, but fine. Let’s say you can do that. Then use that to solve every problem that comes up! Is Captain Kirk pitted against an enemy far more technologically advanced than himself? Go forward in time, get some swell technology, and then use it to defeat the opponent! Or go back in time, give the technology on your ship to the people in that time, and then go forward again and enjoy the benefits of a society 200 years ahead of where it would otherwise be! A combination of these last two techniques (depending on your perspective) is actually done in the series finally of Voyager.
Also, consider the Terminator franchise. The machines go back in time to kill the leader of the resistance whom they can’t kill in the present. The rebels go back in time to stop them. Why don’t the rebels go back in time to stop skynet from becoming sentient?*
*Yes, this ends up happening in the second movie, but it wasn’t the plan.
There are more examples (12 Monkeys, The Butterfly Effect, TimeCop, etc). But I’ll stop here and just say that time travel in movies gets on my nerves. The power of the mechanic is so great that the limitations on it are never internal to the story; they’re imposed arbitrarily by the narrator in such a way as cheapens the struggle of the characters and inhibits our ability to empathize with them.