I have glanced through, but do not claim to have adequately studied, the references provided at the links shown with this post.
I believe the real questions we need to ask ourselves first and foremost may well be:
Q1: "Do *intelligent species* exist on planet earth?" Q2: "Is the Human Species actually *intelligent*?" Q3: "What does *intelligence* mean?"
I don't pretend to be able to provide authoritative answers to any of the above questions.
As to the question in the title of this thread, I would like to state the following:
If any species (*intelligent* or otherwise) does actually exist on any other planet in the universe, then all the species on planet earth would be perceived as 'alien' by that species - just as we would perceive that species to be 'alien' to us.
We do need to learn to resolve the problems we confront rather better than we are doing here as the 'dominant species' on planet earth. (Note: This *dominance* may not persist very long).