The fact that he’s stapled to GLaDOS implies he was more or less fatally wounded by Vader’s sacrifice, but I suppose informing the viewer that the machine has only slowed the process rather than completely halting it could be nice. Then again, that implies that Palpatine’s gonna die regardless if the heroes kill him or not. Sure, the threat of his fleet is more important to the Galaxy, but to the viewer, I think stopping Palpatine himself should feel like the most important thing. He is the main villain of the Saga, after all.