I guess this would be an issue if we actually did start costly new wars.
I can only assume you are referring to Iraq which was actually a war started in 1990 by Saddam’s incursion into Kuwait. That war was never ended.
It was in a cease fire and the conditions of that cease fire were repeatedly violated by Saddam. Saddam had longer range missiles than allowed, he violated no-fly zones, he interfered with and tossed out inspectors. And most importantly he never demonstrated to the UN that he destroyed WMD. That was his responsibility.
I also hope you are aware that it costs three times as much to supply a soldier in Afghanistan than Iraq due to it being land locked. And I hope you don’t think it cost nothing to patrol and hem in Saddam forever.
Our priorities of keeping our citizens and allies safe wasn’t screwed up. That should be our first priority imo.