At least lemmit has a blurb that explains the content comes from reddit. Looking at alien.top itself, they do explain that it’s a page for “Fediverser” which posts content from reddit, but it’s sort of vague - makes it seem like people from reddit are signing up there to do this on purpose, but I’m not sure if that’s really how it works.
And yeah, it’s useless to respond to if the person asking isn’t going to get the reply. I’m not sure why people think auto-reddit spam would be a useful thing for lemmy.