I think this is some sort of modern academia bias. What you say it is true in academia, most things have already been thought and studied and that's why any academic book or paper has a citation in every sentence. I understand why this rigor is important in academia, but is it in the rest of the world?

If I have an interesting thought about a topic and I share it with an audience that is not PhDs, to them it might be interesting and insightful and provoke new thoughts. Most likely yes, someone in the 70s somewhere in the world already wrote a paper about this idea or even a book. Does it matter though? Sharing ideas gets people thinking and the fact that someone else already extensively thought about something doesn't make my thoughts less relevant. If anything, by sharing it I could get a comment pointing me to a book or paper that would help me understand better the topic or expand my ideas further.

I don't think that what's worth sharing are only documents that quote everyone else that already talked about it and their thoughts. That might work if I want to prove that my work is at boundaries of human knowledge or that is the most plausible explanation for something, but if I just want to share ideas then I find it limiting. Not just because it limits the people with the knowledge to write anything to a handful, but also because for those people there is this anxiety of "not worth it, wasting people time" if it's not researched for months like you mention. Share your thought, if some expert will find it wasteful or naive they will not read it, but someone else might and it might open their mind.

This makes me think about philosophy, if you really dig down into it virtually all philosophy ideas were already discussed first by Plato and Aristoteles. You cannot find a modern philosophy thought that isn't in some way already discussed by those two. Should then all philosopher in history not write anything because it was not really an original thought?