EarthBound didn't take place in a dystopia in the traditional sense, you're right, but it was a world bordering on one if society refused to change. It was a world where cultists could mesmerize an entire village, where skateboarding greasers stabbing little kids at the arcade is an actual concern, where the local police force challenges ten-year-old boys to fistfights. It's a world wearing happy colors and bright smiles to hide the poverty and sick shit going on just beneath the surface.
The anti-consumerism and anti-capitalism ties into a general theme of being fake. Everything is fake, everyone is fake, nothing is genuine and what small glimmering specs of actual virtue there are should be cherished, because the world is going to do everything it can to stomp them out. Even if that means murdering them from the inside with a highly evolved Mewtwo from the future.
The anti-consumerism and anti-capitalism ties into a general theme of being fake. Everything is fake, everyone is fake, nothing is genuine and what small glimmering specs of actual virtue there are should be cherished, because the world is going to do everything it can to stomp them out. Even if that means murdering them from the inside with a highly evolved Mewtwo from the future.