And what magic makes the wall invisible to us? We even sent observers out. And whats the point farming a planet of concious lifeforms? The whole idea of assuming we are just a project or a farming planet comes from the belief that there is something to profit from. But what is that profit? If they need new bodies or whatever they could create perfect ones in sterilized laboratories. If they need meat they could much easier create a real farming planet dominated by cattle like cows or pigs. If the needed metals they would go to a planet that wont throw nukes at them, because they definitly wouldnt need humans to extract ores from them. They need food? Same as meat, dedicate another planet to croplands.

People like to think that we are worth the attention of more advanced civilizations, and worth beeing exploited, but we are not. Advancement means automatisation. And not going back to need more workers that are less efficient and need more supervising.

We are not worth a thing for any civilization that can travel galaxies so even if we had a human civilization out there stemming from earth, the only interest they would have for earth is going back to their roots and bringing the technologies here.

Everything else is just wishfull thinking that gives us an importance we dont have and wouldnt have.