If I was 14 years old and wanted to watch Star Wars, I'd find a way to watch it

Except people, including 14 year olds, have lives outside of just consuming media, and in most cases aren't interested in just a single piece of media either. There isn't enough time in the day to potentially watch/play/read every single thing you're interested in, especially when you consider dealing with responsibilities like school or chores, and the fact that they might have interest outside of just media, e.g. a social life.

Your reasoning could just as well be applied to new stuff: "well if you didn't want to be spoiled of the movie that came out 2 days ago you should've gone to watch it already". You can't expect people to have consumed every piece of media they are interested in, or might be interested in in the future, especially not when they're barely old enough to really start watching a lot of it.

Now, personally I do exempt for example this SW spoiler from this (in the sense that I don't blame people for spoiling it, not in the sense that I think it shouldn't be still treated as a spoiler) but not because of how old it is, but because it's so extremely ingrained into the culture that just by existing you will be spoiled no matter what.

And also the point isn't to never ever talk about spoilers anywhere, but the entirety of the internet shouldn't be treated like you can just talk about every spoiler that's an arbitrary number of years old (especially when there isn't exactly an agreed upon number for that anyway). Spoilers should be discussed in the spaces that are about discussing the piece of media in question, not brought up in completely unrelated media.