Information can actually be a good leading indicator provided one knows how to interpret it correctly. I also wouldn't go by the assumption that news is already automatically built into the price - if it did, then price would not change when a news report comes out. However news does get factored in, but there is a time lapse involved, during which one can actually participate.
You make a valid point but you would be surprised how much is out there in the open that can function as leading information.
I base the erratic behavior of price action right after a news release as more of an after-effect caused by market structure and participants more than anything else. True effect happens mostly after the dust settles.
Staying in my lane...