The feat, from the perspective you describe, isn't that remarkable. Humanity has tons of projects that meet these exact standards throughout our history:

> We built something meant to work for decades, knowing the people who launched it would never see the end of the story.

> We pointed a metal box into the dark with the assumption that the future would exist and might care.

> It’s proof that humans will build absurdly long-horizon projects anyway, even when the ROI is almost entirely knowledge and perspective.

The pyramids, the Bible, governments, or even businesses [0] are all human constructs that last way beyond their creators (and their intention), with and without their creator's intention.

> we ever build a civilization stable enough to think in centuries without collapsing every few decades.

This is a valid point though

[0] - https://en.wikipedia.org/wiki/List_of_oldest_companies