The terrain in Death Stranding 2 is not antagonistic. It is indifferent, which is worse. The mountain that prevents Fragile from getting to Lou in time is not trying to stop her. It simply exists, with the mass and the gradient it has, regardless of what anyone needs it to do. The exhaustion of the person navigating it is not information the mountain incorporates. This is the specific cruelty of the physical world — it doesn't know you're trying.