Even the top researchers in the world don't make an impact beyond a tiny bump on the graph of knowledge of their field unless they are also lucky enough to be founding members or on the right side of a paradigm shift.

All you can do is look for places where you can make a contribution and keep an eye out for places that could matter in the future. No one knows what will matter in a few years, but it's often apparent what won't make a difference (the well-trodden path).