I think they changed the story in Dark Phoenix to appeal to a wider audience or to update it for modern tastes. It could also be to add some unexpected twists and turns to keep viewers engaged.
Perhaps Dark Phoenix's story was considered too standalone or didn't mesh well with the established characters and events. Maybe there were creative decisions made to streamline the story and focus on other aspects that were deemed more essential.
Maybe it was to add more excitement and keep viewers on their toes. Sometimes shows need to mix things up to stay fresh.
The reason for the story change could be to introduce new plot twists or to adapt to the preferences of a wider audience. Sometimes, creative decisions are made to make the story more contemporary or relevant.
Maybe they wanted to give it a fresh take or make it more appealing to a wider audience.
Maybe the original actors weren't available or had scheduling conflicts. That's a common reason for cast changes.
Maybe it was to make it more modern and appealing to a wider audience.
Sure. 13 Reasons Why made some significant changes for season 2. This could be to keep the show fresh and introduce new dynamics, but it did deviate from the initial story concept in various aspects.
The story of Dark Phoenix centers on Jean Grey being consumed by a cosmic force that makes her powers go haywire. This leads to internal strife within the X-Men team as they try to save her and deal with the consequences of her power outbursts.
Dark Phoenix isn't an original story. It draws inspiration and elements from the extensive X-Men comic book lore. Many aspects of the plot and characters have precedents in the comics.
The Dark Phoenix didn't kill Mystic. Comics have complex and diverse story arcs, but this specific act wasn't part of them. It's possible there were other confrontations or events involving them, but not a killing.