Write an app, and you've made a new tool instantly usable by any person on earth.

Come up with a simple device and 3d print it.

Lack skills to do any of that - instantly hire unlimited number of experts. Lack knowledge? Access it instantly.

If we're talking about simple low hanging fruit inventions that can be made by a single person, the search space is much larger than the stuff you can do with your bare hands alone in the forest.