I have a pet theory about why we have not detected/encountered any extraterrestial beings:
All intelligent/sentient species go through roughly the same process of scientific discovery, eventually getting to a point amounting to “what happens if I press this button...” and the entire planet evaporates, happening before the species achieves self-propogating interplanetary/stellar travel.
Recall the bets taken on whether the first H-bomb detonation would set the Earth on fire.
You just might be onto something there ... but if there have been more than our intelligence, arise on another planet, somewhere, then there probably have been so many such events that eventually one planet’s smarties would have anticipated the dangers and avoided them ... so why are we still not in touch with them? And why wouldn’t they go around the unioverse trying to prevent such planetary suicides?