I get your point, but totally agree with it. I think Congress lacks the backbone to declare war. And even if we did, I have doubts that we would do what was necessary to win. The one case where we did "win" was Iraq War II, where we deposed Saddam and brought about regime change. However, I think almost no one would call what followed a true victory. Grenada and Panama might be other, smaller scale, examples.
I thought Iraq War I was a better example of winning in terms of achieving our goals (primarily the liberation of Kuwait), and it is no accident that like Korea it was done as part of a large multinational force. When we go it alone or with a few select allies, it doesn’t work as well - either uninvolved countries are critical of it or outright supplying the enemy. Arab countries assisted in Iraq War I to restore some semblance of the status quo (and NOT depose Saddam, seen as a stabilizing force in the region); at the time they warned us they didn’t want exactly what unfolded after Iraq War II.