The Undertale universe still exist and hasn’t been conquered by communism. This universe has a protective barrier which only pure capitalist humans can pass through
Anarcho-Capitalism and Communism keep each other in check, y'know. If one where to reign supreme, then the balance the universe would topple, leading the universe to be either a chaotic mess (AnCap), or a heat-death-esque mototony (Communism).
Oh wait, communism has reigned several times.