We have not discovered alien life on other planets. Our telescopes are not sensitive enough to pick up on weak artificial radio emissions from hundreds of light years away. And the sky is too broad for us to listen to all areas of the sky at all times, we are only listening to a tiny fraction of the sky at any given moment. Aliens, however, are much more likely to be listening to planets like ours, given how advanced their radio telescopes can get, meaning that we could indeed be discovered by aliens before we discover them.
Our planet, however, cannot be found yet because of the speed at which light travels and how recent our technological advancement has been. Our radio emissions, such as radio broadcasts and nuclear bomb activity, have only started appearing in the 30’s and 40’s. Our galaxy is 100,000 light years across. Even if the nearest technologically advanced civilization is just 150 light years away, we would still have another 70 years until we could be found. And, unfortunately, we are not likely to be visited any time soon because of this. Our galaxy is so vast and the amount of stars in it is so ridiculously enormous that they have no reason to come here unless there was something specifically interesting about this part of space, like signs of a new intelligent life form.
But our discoverability, or lack of it, is something the aliens managing earth depend on. Part of the requirements of the earth project is that we would be completely isolated from alien influence. They need us to be disconnected from the outside universe so their own presence and influence would remain secret (to us), and that our development won’t be affected by the availability of more advanced technology during the early stages (competition would be hard to beat). So they actually have a relatively small timeframe to progress our technological development, because of the necessity of development of radio and nuclear technologies, to be prepared for assimilation with the outside universe. This is why technology has advanced at such an unimaginable pace in just the past 100 years compared to the rest of human history, and keeps advancing at an exponential rate. But one may ask, if they don’t want us to be found, wouldn’t the show I am in reveal our location? It wouldn’t. No actual coordinates are being revealed, and any other method of deciphering our location from clues, such as our visible constellations and the movement of visible stars across time, would be futile because of the great number of stars in our galaxy and the too numerous possible results from such a search.
So as you can see, the aliens and us are at a race against time. The clock is ticking while we progress our development to be prepared for the time of our introduction to the greater galactic ecosystem.