It's never aliens — until it is
It might be worth taking a deeper look at the sociological parameter. aka John B. Calhoun's Mouse Utopia Experiment: We just die out because we stop reproducing.
Also: We don't have to die out entirely. Since we have used up all easy to access fossil fuels any destruction of our current hight tech would mean we can never get it back.
Like Tamriel we would live in an eternal middle age society. Looking back at the “ancient humans” who commanded now forever lost “magic powers”. Scavenging through the ruins left behind unable to understand or repeat the magic.
Will We Ever Find Alien Life? | Space Time
The silence of the galaxy and the resulting Fermi Paradox has perplexed us for nearly 50 years. But our most recent surveys of the Milky Way finally allow us to draw scientific conclusions about the depressingly persistent absence of aliens.