Life has existed here on earth for at least 3.2 billion years, and our species of modern humans have been around for 200,000 years. Yet only within the last 50 years are we able to send spaceships to the moon and beyond. If some intelligent aliens exist and they were told that there are intelligent beings on earth capable of communicating with radio waves, they would not be able to find us even if they know where we are exactly, if they arrived on earth a hundred years ago, a thousand years ago, or a million years ago.
The universe is huge. It takes us years to travel to other planets within our own solar system. The next solar system within our own galaxy is beyond our reach. Therefore even if intelligent beings exist elsewhere in the universe, we simply cannot find them or reach them with our current technology. That means they will have to find us. To do so, they must be a lot more advanced technologically than we are, and for that to happen, it may take billions of years of evolution to happen in a distant planet. The likelihood that they evolve such high intelligence within the same time frame that we evolved our own intelligence and technology is infinitesimally small. Even if we and the aliens evolved intelligence at the same time, it still won't work, because they would need time to come to us. Our closest galaxy neighbor is Andromeda and it is 2.5 million light years away. So, unless intelligent beings exist within our own galaxy, it will take them 2.5 million years at least to come to us for a visit, even if they can travel at the speed of light. Even if they can travel at the speed of light, they would need to start their journey 2.5 million years ago to reach us now. If they started their journey 100 years earlier then they will only see some model Ts at best, but no spaceships or televisions or computers.
Because the universe is so vast and because there are so many galaxies (billions) and because there are so many stars (billions in a galaxy), the chance of life evolving elsewhere is high. However, because the universe is so big and because galaxies are spaced so far apart, the probability that any intelligent life evolved just at the right time and then come to us for a visit is so small that you are more likely to win multiple pick six lotteries in the same calendar year than you are to meet an intelligent space alien.