At this point there has to be other civilizations out there right? There's just too many systems for us to be the only ones.
For example, how about interplanetary scale lifeforms akin to boltzmann brains, where each analogue to a human neural impulse takes minutes or even days to zoom across empty space?
What about dark-matter based life? If dark matter composes of 95% of our universe, could there be a whole different set of dark matter based physics, life, and technology, where the intelligent dark-matterians speculate about the mysterious 5% of the universe which interacts with these strange oscillating electric and magnetic fields?
I know it's unlikely and that given our sample size of n=1 we can only be confident about organic lifeforms, and it's our best bet to search for similar life -- but I like to imagine that thousands (millions?) of years in the future when we find other kinds of life, it'll be obvious to everyone that life exists in all possible ways and they'll laugh at us 21st century folks for believing that just carbon could self replicate and think.
The idea of "dark chemistry", whole not whacky enough to be immediately discarded, is highly exotic.
They would have a hard time figuring out the existence of electic and magnetic fields. They wouldn't feel them. And their devices wouldn't feel them.
They would be able to notice 5% of mass by gravitational interactions only. They wouldn't be able to see how magnetic fields reconnect on a surface of a star and conclude that it means there is some unknown field at work.
So to think, they probably have their own dark versions of magnetic and electric fields.
As we are watching AI with concern on our own planet, what if that is a common bootstrap. Carbon based life creates silicon/metallic 'life'. And if that is possible, who knows what that would bootstrap itself into in the future.
Intelligent life? Probably, if there's life it's bound to happen some percentage of the time.
Intelligent life that has mastered exploring space enough that we could theoretically communicate with each other if we both looked at the right spot? I'm less convinced, but it's impossible to say with the sample size of 1.
Intelligent, spaceflight capable civilisation that's close enough that we could ever make an actual, physical contact without the trip lasting generations? Unlikely.
Show your math?
The universe is expected to be teeming with purposeful matter eventually.
So yeah, life must be out there. But maybe “there” is very very far. Possibly many million light years away. In other words, in a universe with billions of galaxies containing billions of stars, life is likely not very plentiful. I imagine encountering any element besides H/He is usually a discovery (more so if the element is higher up in the periodic order, such as the ones needed for our kind of life).
Then again, there is so much we don’t know. Like dark matter (anti-proton/electron/neutron/*). Maybe there is life that exists in anti-everything - (anti-carbon, etc). It won’t be very good if we ever encounter them (our carbon based bodies and anti-carbon based one will collapse on encounter, emanating a staggering amount of energy).
It appears from spectra that the chemical elements produced by stars are the same everywhere. If so, then the possibility of material life exists everywhere in the universe ... where conditions permit. It's down to the presence and concentrations of the various elements, the temperature and stability of some fluid medium that can bring the endless potential combinations into contact, and a lot of time. (Calculating the odds is an exercise left for the student.)
That would explain why we don't see anyone else.