The Fermi Paradox wonders why we don't see aliens, based on the Drake Equation.
-One possibility is that they live way longer than humans. If you were an insect with a lifespan of a few days, the chance of meeting a human is less than if you were an elephant with a lifespan of 60-70 years. Also, if aliens dropped by, say 100.000 years ago, we would have no evidence of that now.
-Another explanation could be the Great Filter hypothesis, stating that any civilisation reaches a point were energy/resource consumption, due to population growth and technological advance, leads to irreparable climate change and ecological collapse on the planet, and thereby extinction of it's population, before they are able to develop interstellar travel.
-A third explanation is that the Universe is so enormous that the chance of some alien explorer finding Earth is minute.
I'm afraid that my work has shown me that #2 is very plausible, but I'm not quite as pessimistic as this guy (yet):
The man who wrote the book on living off-grid in the city plans to retreat to a rural bolthole, saying eco-friendly progress has not kept pace with the speed of climate collapse
www.theguardian.com
On the other hand I find the current optimism somewhat naive or delusional, maybe even a deliberate denial of reality. I have always had one principle towards science, being that whatever you discover you share it, no matter how ugly it looks. I'm not so sure anymore. Maybe it's better to keep the illusion while it lasts.