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Universals of the universe:

"From this premise, Kershenbaum says, it follows that life on other planets will have evolved, if not along the same lines as life on this planet, then at least along lines that are generally recognizable. On Earth, for instance, where the atmosphere is mostly made of nitrogen and oxygen, feathers are a useful feature. On a planet where clouds are made of ammonia, feathers probably wouldn’t emerge, “but we should not be surprised to find the same functions (i.e. flight) that we observe here.” Similarly, Kershenbaum writes, alien organisms are apt to evolve some form of land-based locomotion—“Life on alien planets is very likely to have legs”—as well as some form of reproduction analogous to sex and some way of exchanging information: “Aliens in the dark will click like bats and dolphins, and aliens in the clear skies will flash their colours at each other.”  

https://www.newyorker.com/magazine/2021/01/25/have-we-already-been-visited-by-aliens

“It is quite conceivable that if we are not careful, our civilization’s next few centuries will be its last,” Loeb warns. Alien civilizations “with the technological prowess to explore the universe” are, he infers, similarly “vulnerable to annihilation by self-inflicted wounds.” Perhaps the reason no one has shown up is that there’s no one left to make the trip. This would mean that ‘Oumuamua was the cosmic equivalent of a potsherd—the product of a culture now dead.