[akomtu]

A much bigger elephant in the room is the fact that nearly all mass of the universe is made of dark matter and we have no clue what it is.

It seems plausible to me that by the time a civilization can quickly travel to other stars, it becomes so different that it doesn't need to interact or even be visible to advanced monkeys on a distant planet, just like we aren't really striving to talk to exotic monkeys on isolated islands. And the only reason those exotic monkeys and birds haven't become our food, like cows or pigs, is that there is very little protein on their bones (speaking bluntly).

We also wonder why we don't see alien activity in radio spectrum, while at the same time we use encryption to make radio wave communication indistinguishable from noise. More advanced civilization might have learnt that not getting noticed is vital to survival, so they scramble all signals. That background microwave noise might be those signals scrambled.