We couldn't communicate with the most advanced primates from a million years ago. A civilization a million years past ours would be unlikely to want to talk to us. The average star in our galaxy is a billion years older than our sun.
You can only communicate with civilizations near your level, which are inherently much rarer.
We aren't old/developed enough to be interesting to talk to.
Our brains may just be made up of lumps of neurons, but we can break out various capabilities we have:
* language * tool use * memory * ability to think about hypothetical situations * ability to think about abstract concepts * theory of mind
We can think about what alien creatures or civilizations are like that lack them. A civilization without tool use, a civilization without language, a creature with no memory.
But thinking about capabilities we don't have is really hard, because, you know, if they exist, my brain isn't equipped to think about them.
I can think about having a perfect memory, or being able to think about N things in parallel, or being able to learn things by directly copying the information to my brain. Are those good enough to be new capabilities, or are they just minor variations of the capabilities I already have?
Suppose there's some property of physics that looks like random noise to us (maybe like a TV looks like random noise to a cat) but to a different species they see it's something they can model and understand while our species just ignores it?
Of course the TV thing was just an example, cats don't pass the mirror test (If you put red dye on one part of their face they show no interest in how their face looks different when looking in a mirror).
I've never heard of someone filming a video for cats in 4x slow motion and asking people to play it at 4x to entertain a cat, so I'm assuming this experiment has been tried and doesn't work, but I'll give it a shot.
(It occurs to me I would need to confirm the Android Youtube app supports 120 FPS otherwise I'd need to play something through a PC).
An ET civilization will certainly judge us at that "aggregate level" (However that comes about)
Based on what? Just because a civilization is extremely sophisticated doesn't mean we have nothing to offer.
We still study primates and ants. Hell, we even desire that we could communicate with chimps and dolphins.
Communication is impossible with primates and ants simply because they lack the hardware to engage in abstract communication.