I would say that modern wars are 'short and winnable'. It's the nation building part that isn't.
War in Afghanistan (2001–present) - https://en.wikipedia.org/wiki/War_in_Afghanistan_(2001%E2%80...
When specifically did that war end and nation building begin? Who won the war?
EDIT: Is the Global War on Terrorism / Operation Enduring Freedom a "war"? It certainly feels like an never-ending war.
And https://en.wikipedia.org/wiki/Soviet%E2%80%93Afghan_War before that.
And a long list even before that.
I left out the first because top-level thread comment concerned European 'Great Powers', and because I wanted to give a specific counter-point with the major world superpower.
I think all powers know this full well hence why they never engaged in direct conflict since WWII.
Wars since WWII have been limited wars against much weaker enemies and proxy wars.
But time is always on the side of the defender, especially against overwhelming force. You beat a sprinter by making it a marathon.