Depends on so many things. Situations like a certain death in FF7, which has essentially reached meme status at this point, I'm not bending over backwards to keep a secret anymore. Or the movie Se7en, where the box scene and ending twist are infamous to the point of being separated from the movie. But generally, if a conversation doesn't require me to spoil something, I won't.
It's tough, there's no real rule book, so people kind of need to play it case by case, but there are definitely situations where I'm in the camp of "yo, this shit is 10+ years old and the spoilers are infamous, I'm not gonna dance around it".
Spoiler culture is one of my absolute least favorite things. Some people are so vehemently authoritative about it. That said, people are human, and while I don't think it's fair to assume that everyone has seen/played the same things as you and you should go around talking freely, I also think people need to chill the fuck out a bit and realize finding out certain plot elements of something that's been out for a good long time, but you haven't played yet, isn't something you can realistically get angry over