Wait, who is claiming you could 'see China' if the earth was flat? And you could see the end of the hallway in person.

It's a flat earth joke.

One of the so called proofs for a round earth is that ships are disappearing on the horizon, implying that on a flat earth you'd be able to observe ships until they reach the opposing shore and thus you'd be able to also see far away places like China. Just like you can see the moon.

The meme shows you that in reality you cannot look that far. And no, you also couldn't see the end of the hallway in person if it is long enough.

You can provoke a similar phenomenon with two mirrors to create an "infinitely repeating space" inside the mirror. At some point you just can't see anymore, because it gets too small for the naked eye.

If you take out a telescope you can see farther. Both in the hallways and also ships that seem to disappear into the horizon. The reason your naked eye loses sight of them is because they simply became too small to perceive. That's exactly what the horizon is. It is not because the earth curves away from your sight. Not even in a round earth scenario. At that small of a distance the earth doesn't curve yet.

Luckily the moon is really large, so you can see it even though it is far, far away.

So essentially the meme is mocking people that are ill-equipped to disprove flat earth. In my opinion that's the whole flat earth joke, too. Showing that your average person cannot even disprove flat earth. Essentially revealing that most people follow science exactly as uncritically as they follow(ed) religion. The authority™ said so, so it must be true.