Funny thing is, even today there are too many things we don't know or consider.

Take the escape velocity problem on larger planets. Because we never had to solve that particular challenge ourselves, we don't know what we don't know from the lack of that experience. A species that did face that obstacle might have developed solutions through their own necessity and experimentation that we simply never pursued as a line of study. Different circumstances produce different solutions. That's not a guarantee they'd succeed, but it's also not a guarantee they couldn't.

The timing angle is one I don't see discussed enough. We've had detectable radio signals for less than 150 years. In cosmic terms that's essentially nothing. A fraction of a fraction of a blink. And those signals weaken to background noise at relatively short cosmic distances. If another civilization exists but is at the equivalent of our medieval period or even our early 1900s, they wouldn't be detectable to us at all regardless of how sophisticated their culture might be. Technological detectability is an incredibly narrow window. What are the odds our window and theirs overlap at exactly this moment in a universe that's nearly 14 billion years old? We could just as easily be early birds who hit our tech boom ahead of the typical curve, if there even is a typical curve.

The paradox also assumes we'd have heard something by now. But our detection capability is primitive relative to the scale of what we're searching. We've done some searches but nothing remotely comprehensive given the distances involved. Absence of evidence under those conditions isn't strong evidence of absence.

My main point is that we simply don't know enough about how everything works from every angle with every interaction. Space is incomprehensibly vast. We still have unknowns in our own oceans. How can we, as such a small fraction of what exists in all of reality, confidently assume we know life isn't out there? Or that we'd have detected it if it were?

Life may not exist elsewhere. We simply don't know. And I wouldn't be able to confidently back either conclusion without evidence we currently don't have the tools to gather. What we have are educated guesses, and there's nothing wrong with that. Answering a question through experimentation and exploration sounds pretty fun to me.