My parents met each other at a scifi con. I was literally born in fandom (want to remind the younger audience here that the earliest known scifi cons were in the 1930s, have fun with that).
Sure, there will be fans who will interpret my work and characters in ways I would never ever want it to go. But that's not just fandom in general, but academics. How often have authors argued with critics that they understood the themes of their own books wrong (extra props to the arguments Vonnegut has had!)?
I'm sure I'd first be on a wild high that it existed in the first place, but if I ever came across fan works I didn't care for? I'd hope I treat it the same way I treat fan works within the fandoms I do participate in. I leave it alone. Sometimes I find works better than the original source. Sometimes I find great work that in some spades, I would considered out of character but only because what elements of the characters I find most important vs the writer of that fanfic were different. Those are fantastic examination studies honestly.
Fandom is where I explored my gender and sexuality among other things. Things that I'm 100% certain were OOC for the original creators but dammit, queer characters were not allowed to exist, so all I had was a subsection of fictional fiction of what is fandom. I'd feel stupid hypocritical if I told people not to play their own "what if"- even if it is het/cis stuff. Sure, it would be super OOC to me but also- hey, I'm a huge fan of uchronia and I'm always always down for a good "what if" break down.