For how cynical you are about humanity, you've got an absurdly anthropocentric idea of "littering". Humans have left a negligible amoung of waste on the moon, yes. To the universe, that's pretty irrelevant: a bit of inanimate matter on a huge chunk of inanimate matter, and nobody there to care about it one way or the other. To a civilization way more advanced than ours, these'd be some fascinating artefacts on an otherwise boring world. It takes a human to go "eww, astronaut poop".
It's fascinating. I used to joke about it, because I thought it was awesome, when I suddenly realised people were taking this extraterrestrial littering thing seriously.
If there's ever a settlement, human or otherwise, anywhere near a crashed rocked stage, the wreck will be a monument, you wouldn't be allowed to touch it, I'd reckon you wouldn't even be allowed to put it inside the pressurised part of your habitat or step anywhere near it. Cleaning it
is what would be tantamount to littering and contamination.
Not only there is no biosphere or natural wonders there to disturb, but these objects are so rare and unique that they wouldn't disturb anything even if there was. It would be no different if ancient aliens crashed a spacecraft inside a present-day rainforest, we'd cut the trees around it to expose it, and it will be the polar opposite of waste. And if it was buried under a house in Pompeii, we'd disturb part of the ruins to open access to it precisely because it was more unique and rare.
On an semi-related note, even exaggarated end-of-the-world fictional works
can show appreciation for technological junk in a middle of a rainforest.