No I think that "everything poops" is absolutely perfect. Poop is entropy, and everything turns into entropy eventually.

It might not be traditional poop as we know it, but the point is, no matter how far we go one day, no matter what/who we meet out there, no matter how much we advance, there will always be waste to manage.

Waste might be literal poop, waste heat, spent uranium, used oil, slag from a smelter or whatever. We might be perfect recyclers one day, and we might repurpose almost everything, but there will always be a little bit of "poop" left over to manage.