"Nothing was accomplished on either side"
What was accomplished was the survival of protestant Christianity. Would Northern Europe have been protestant if they had done nothing?
Yes, survival of Protestantism, and survival of Catholicism. Presumably that was what God wanted to happen, although I don't like to second-guess providence. But it was a very bloody thirty years, to end up right where they started.
I'm not knocking Gustavus Adolphus. But I have read fairly extensively about the Thirty Years War, and it was not a happy affair, especially in the German states. Much of it deteriorated into armed bands who went looting and raping and burning all over the countryside, with no particular commitment to the causes that began the war.
Of course, nothing ever remains the same in history, and no doubt there were good as well as bad effects.