The arguments some people make is that if it’s likely there’s so many other civilizations out there, then why haven’t we found any evidence of any of them? You have Great Filter and Dark Forest theories that try to explain it, both of which would likely be very bad for humanity.

But it all forgets that we really haven’t searched much of even our own solar system in incredible detail, so it’s very possible we either haven’t looked in the right places, or don’t have the tech in place to see civilizations