I believe that Aliens likely know we exist, they are just waiting for our civilization to evolve or otherwise reach a tipping point.

According to almost every AI researcher, the Technological Singularity is essentially guaranteed to happen in some capacity at some point in time. Due to this, it is probable that any space-faring civilization has also achieved a technological singularity, otherwise their progress in developing and using space technology would be extremely slow, as we can see with humans.

The Technological Singularity is likely the moment in time that a species evolves from pure biology to biology/machine hybrid. The cyborgs will leave biological humans far behind in terms of intellect, physical health, and nearly every other capacity.

To the Aliens, even the peak biological human is a puny ant. They are waiting for us to reach the "accelerating intelligence / technology" stage and observing us at least up until that point to
1. ensure we don't fucking blow ourselves up
2. observe another civilization reach a massive evolutionary milestone

It is an unwritten law that any civilization who meets a weaker or less-advanced civilization will end up wiping the inferior civilization out of existence via genocide. This has occurred in every interaction between civilizations with great disparities. Aliums likely know this and have studied it, so they realize that they cannot ETHICALLY contact humans without ensuring the humans are at least near the same level.