Something else I see people keep forgetting: between humans and Eridians, we are the astronauts. And we are good at it.
Eridians' perception of the world relies on something that is completely absent in space — sound. They haven't been looking at the stars their entire existence the way we have. Their concept of aliens might only be as old as their discovery of astrophage. They made a bad ship, because it was their first one ever! Rocky himself says they rushed it, and that multiple (vital) things broke. Their mission was just as much of a Hail Mary pass as ours was — they had no idea what they were doing, if they could even travel in space safely. And, as it turns out, they couldn't.
Humans are the ones who have been doing it over multiple lifetimes. Mary is state of the art. We've been space farers longer than most humans have been alive. We can actually see through space. We are more likely to survive exposure to the void. We can encase our lighter, more flexible, more mobile bodies in a material that lets us walk outside of our ship, and, to a degree, we can get our bearings out there in a way Eridians just can't.
Eridians are not looking at Mary and thinking she's a bad ship. They are not thinking humans have no idea what we're doing. They are looking at this species that can walk in the stars, have been perfecting machines to take us to them for decades, have been dreaming about them and mapping them and naming them for millennia, and used all of that to save them, and thinking, wow.
This, like I think they won't understand why we made it out of aluminum instead of anything else but if aliens showed up on earth in a fully functioning spaceship made out of cardboard, that was capable of climate control, air and water recycling, and radiation shielding, I'd be pretty damn impressed they did that and excited to see what they do with like. Metal.
Like Xenonite has tensile strength so insane you can hold massive amounts of pressure back from the void of space using entirely flat panels. Imagine what Earth can do with it once humans apply our "never put a corner on a pressure vessel" knowledge to it
