Is it really a spoiler when something has been around forever?

Ok, so I’m the type that doesn’t mind spoilers. I can’t imagine how stressful my life would be if I lived in fear that someone might “spoil” something for me if I am not fast enough to read it/watch it/ etc.
So my question arises from that thought, can you really blame someone for “spoiling” something that has been around for years? As an example, a lot of people are just watching the Fruits Basket remake, so they *dont* want to be “spoiled”, but the manga ended in 2006, the new anime is going to adapt the whole thing, meaning a lot of those manga-only secrets will be no more. In my very personal opinion I don’t think people should get angry if someone “spoils” something for them that has been around for 20 years. I get if you don’t want to know who dies in the latest episode of x hot series, or book, but to b*tch and moan that people are “spoiling” stuff that’s been around a long time?