Yes, shoe inserts work. Some people seem immune to foot problems, but for most, the factory shoe insert is insufficient. Either the wrong shape for the user's foot, or too flimsy to provide adequate cushioning. I almost always replace the factory insert with something that works better for me, even when the shoes are new.
Also, it's normal for running/walking shoes to break down after a few hundred miles. When I was running a lot, I would buy a new pair when that started to happen, and repurpose the old pair to using for yard work. Anything you use that often is worth investing in, and there's no reason to push your luck in a pair of old shoes. Too easy to get some sort of minor-seeming foot pain that may or may not turn out to be so minor.