My take on reading fanfics of series, shows and movies that I have not yet or will not watch/read: Why not?
It's brought to my attention that people are baffled, annoyed or even offended by this. Yes, it does get confusing sometimes and I do comment when I'm confused.
In defense, I will say not everyone has the time or the interest to finish whatever they're reading and watching so not everyone will be consuming a fic with the same context. It's their fault if they don't have the knowledge beforehand but who cares? I don't expect authors to write a summary of what they're making a fic about. It's my fault if I get spoiled and if I'm reading a fic without context, I frankly don't care if I see a spoiler or something I don't know about. It comes with having no idea what this fic is about and continuing to read.
If you still get annoyed and start shouting in the comments why someone doesn't finish a series first, I'm sorry to say we all consume art, media and content differently. I am not you and you are not me. Some people skip to the ending, I skip to the fanfics.
I actually got into a few series and watched/read them later on because I read fanfics of those series and liked the premise it had. I also avoided some shows because of how the fanfics I read highlighted the worst qualities of the show. Sometimes, I didn't like the fic but started reading the series to see and judge for myself how it really is.
TLDR: Who cares if you don't know the context behind the fanfic you're reading about because you can choose however you want to consume art, media and content.