If you’re writing cover for mass movements? Run it by someone else first.

If you’re talking to people? Don’t dumb it down. Just be open to explaining words and concepts. People like to learn. Provided you aren’t being condescending or gatekeepery, it’s not a problem. (Unless you talk like Zizek or Jameson, in which case, don’t.)

Actually, Jameson and Fisher provide pretty good contrasting examples. Jameson came up with the idea of postmodernism as the cultural logic of capitalism (in the book of the same name), whereas Fisher built upon it with the notion of Capitalist Realism (again, in the book of the same name). Try reading both of them, and you’ll very quickly get an understanding of what accessible language does and doesn’t look like.