Time is a necessary part of storytelling. Because without time: nothing happens. Things happening is what lets you know time still exists, even if it's abstract. Usually stories handle time in a beginning-middle-end structure, and that makes a lot of sense because that's how the world works. But sometimes stories will have jumps forward and backward. Suddenly you're ten years in the past or thirty years in the future for a full chapter or for half an episode, and then a little bit later you're back in time with the rest of the story. It gives context, it gives consequence, it can give confusion. Do you like it when stories skip back and forth in time, or would you rather just have one specific timeframe of sequences without flashbacks and flash-forwards? Is it good sparingly, is it better when it's used constantly (like This Is Us), or is this a way for a storyteller to say goodbye to their career (or at least your viewership/readership)? Have you had any success with making long flashbacks and flashforwards work in your own writing?
So, I'm gonna try to see if I can be completely honest. Rarely ever will I do a time-cut, and it's usually only a memory of a similar moment, or a "trigger" caused by something entirely unfamiliar. My newer story does this in the first chapter, but only for a single paragraph and for a little bit of lore. So, I don't like it, but it can help for revealing lore that wouldn't be known otherwise. And it can also take away from the action for a moment of peace or to reveal what no one else knows. So, in the end, useful, but not really liked.
Flashbacks can be useful, if used accordingly and sparingly. Time-jumps are useful for skipping mundane stuff that can be summed up in a single sentence. Not all of life is a nonstop train of excitement and drama; those actually tend to happen in between the mundane majority of life-time. The key, again, is knowing where to place them and how to talk about them while not actually doing so.
If used correctly, time jumps can work wonders in a story. If you don't want a particular motive of a character revealed, then hiding it behind a back story is a great way to keep it secret while still not being disjointed. Time jumps into the future are harder to pull off. For a future time jump to really work, it has to make sense to time jump. Either a lot of mundane things are happening or you're jumping in between plot points/plots. However, to use past time jumps earlier in the story that has already been written to me is just lazy. If something wasn't clear the first time, then it should have been reworked (that is to say unless it was intentional like viewing the same events from a different frame of reference). I do plan on using time jumps in my story, however only to skip mundane travel sections of the story. Most of the story is first person and to try to use time jumps would be even more disjointed for a first person perspective than any other perspective. On the other hand, I am going to have several sections where the main character sees the past through complicated methods but I don't consider those time jumps since there is no out of body experience that takes place, it all happens right before the main characters eyes.
It really goes down to how it's presented. Flashbacks can be good as long as they're an important part of the story and are implemented well, not "suddenly, in the middle of the final battle, he had a flashback of an incident he had with his little brother who taught his determination"... in those exact words. Time jumps are good when placed well, such as the sudden chapter flashbacks in Holes by Louis Sachar, for example. Time jumps, when not pointed out (please do not say "Time Skip" in the middle of a story, it ruins the flow) and not transitioning to an awkward place, can also be used to forward the story.
