Recently the Central Intelligence Agency (CIA) admitted that they were responsible for many of the UFO sightings from the 1950s and 1960s. Those were secret spy planes, not aliens.
The case against visitation by aliens from other planets grows stronger with each historical fact and new technological discovery. They're not here, they haven't been here, and it seems they aren't coming anytime soon.
Scientists have calculated that the probability of advanced life on other planets is extremely likely. For example, the Milky Way galaxy alone contains 8 billion earth-size habitable planets.
So the probability is that advanced alien life does exist even though we have never seen it and have no direct proof of it.
One of the leading theories explaining their absence here is the great distance between the galaxies and planets and traveling those distances in a reasonable period of time (the speed of light and all that) may be insurmountable. I'm not sure I believe that. I suspect there is a workaround. This isn't the reason aliens avoid the Earth.
I believe aliens know we are here on this Earth. They know about this planet and the people on it. Somehow, they have a way of knowing. And as a result of knowing something about us, they choose to avoid us.
The primary reason aliens avoid the Earth is because this planet is a ghetto.
We as advanced creatures have nothing to offer them in any positive way. And our planet has little if any of the natural resources they may crave, and what we do have that they may need they already can find in abundance locally to them.
Aliens don't respect our leaders or humans in general. They dismiss us as unworthy of interaction with them, not just because they may already know everything we know and more, but because we represent an intellectual path leading the wrong way, to disaster.
And surely they have calculated the dangers of communicating with us. They may be in a physical state where they are vulnerable to harm from us and our weapons. Therefore they need to be careful with whom they associate. And they are well aware of our propensity toward violence.
They don't need us, they don't want us, and we can't help them with anything. Not even as a rank member of some sort of inter-galactic federation, if there is one. We don't even qualify for that.
We haven't yet found direct evidence of other civilizations, and I suspect that is a deliberate attempt on their part to hide from our view. Having decided to avoid communicating with us, they want to limit our ability to detect and communicate with them. Such interaction can only lead to trouble, they surmise.
How much do we need to worry that we are considered persona non grata by alien civilizations? Hard to tell, not knowing the landscape of advanced life even in our own galaxy. A humiliating assessment or wear it like a badge of honor?
And their assessment of us as a ghetto filled with worthless creatures. Is it true? Are they correct in that judgment? What evidence could we provide to them to the contrary? How would we prove ourselves as a worthy partner for other advanced civilizations?