In the early or mid 2000s, I remember watching an anime episode (or maybe movie) where 3 US astronauts get transported by some space macguffin to the distant future and are found by a post-humanist ship. The plot revolved around them being confounded by the future such as the human lifespan only lasting through peak productive years and their entire life being regulated by the government. Meanwhile the future citizens think the astronauts are basically barbarians and blame them for almost destroying the Earth during the 21st century which led to their post-humanist society.
At the end of the episode the space macguffin shows back up and teleports the astronauts again. The End?
I thought the show would of been on Adult Swim but I see nothing like it. Watched it in English, very late at night and the animation was late 90s, early 2000s style.