Despite joining in on this thread, I wouldn’t say that fans outright ruin anything permanently. In my post above, I describe an experience where I was put off by Undertale–every joke and precious bit of the game was blasted all over social media to destroy its impact before I could even get hands on it–but I later came back to enjoy the game just fine.
I think that fans can make it difficult to get into something. I’m loath to post about wanting to watch a new show or play a new game that I know has a rabid fanbase, because I’m waiting for that response that is like “fuck x you need to watch y first” or “ridiculously specific thing about game that sounds like a pain in the ass but is apparently the only way to experience it”. There are people out there who will react with shock or even disgust if you get into something really late, which is exasperating (i.e. “look at all these bandwagon fans jumping on, we’ve known about this for a while”).
You can still shut fanbase feedback out, but sometimes it is that one thing that pushes me away from experiencing media at the moment. I’m just like, you know what, fuck this–not because of the thing itself, but fuck this. Hopefully I’ll come back to the thing later though.