Confluence used to be built on top of pretty standard plain wiki markup that could be edited without being forced into a bad visual editor, even easy to edit in an external text editor to not have to spend so much time in the web UI at all. I remember having an Emacs mode for it installed.

Looking this up now, Wikipedia says the wiki markup was abandoned already in 2011. Not that I think Confluence was ever a great wiki, but at least having pages that were backed by some resonable plaintext markup was much better than not having that.

You can’t copy and paste markdown, nor can you use it in the native way in confluence. They have third party paid plugins that can do it.