That's funny. I'm trying to lurk more and say less. Inertia plays a big part.
It doesn't matter if everything has been said before. Literally my most viral posts have been repackaging what someone else said to me. I find that my original thoughts might be a little too deep or required too much prerequisite knowledge. But you can literally just grab something from a favorite book, rewrite the main points and people will love it.
We're in an era of information overload. People on social media want information, but they don't want to actively chase it, and expect it to come to them. You can always just summarize what you learned from someone else.