i feel like there's a difference between the author themselves doing the rewriting (which i'm fine with, because you're essentially just publishing a new edition of your book), and someone else who just happens to own the IP doing the rewriting (which i'm a bit uncomfortable with, regardless of what exactly is being changed).

it's like if a painter adds something to an already-completed artwork that they had painted and then describes the result as a refined version of the painting (fine), vs when someone who just happens to have bought the painting adds something and then argues that the resulting painting is now the "official" version of the painting, while still naming the original painter as the creator (not fine).

>Didn't the Victorians (and people before that) rewrite Shakespear all the time to fit the current vibe?

Yes, and they are now generally mocked by today's critics for doing so.