Or it’s just looking at basic storytelling. Things get set up, then paid off. If something is established one way for 8/9 films, a sudden change at the end of the last film will make people question it.
The modern film trope i dislike is prioritising looks over story. Changing the colour at the last minute just because it looks cool and different has no real merit to me.
Someone brought up the changing of saber colours, and that’s a bit different: because it’s a prop. We are already accustomed to props, costumes, and even lightsabers specifically having various colours across all nine films. Making this change doesn’t impact the story with questions of “why is it different?” That’s been established and set up.
When it comes to powers, especially in a scene where under-developed powers are are already a major focus, adding another new and unestablished element will distract away from what’s going on. If sucking that much life out of them gave him so much more power that things have changed, why does he need them to kill him to get a new body? He’s beyond rejuvenated, what’s the point? This type of change gets in the way of storytelling.
Again, if you changed it everywhere, so the power was established as such, that would be different. But introducing a new, unexplained element that makes us question the motivations of the villain in the third act of the 9th film… that’s just bad storytelling.
And we can play the ageist game of “back in my day…” or whatever. That’s irrelevant. The purpose of the scene is that Palpatine gets rejuvenated. If he goes beyond rejuvenation to more powerful than before, his motives for the rest of the film no longer make sense. It’s always been implied Palpatine was stronger than he let on in other films, and he didn’t do the crazy antics like he does with the fleet, because he never needed to and it would go against his goals in those films.