We haven't seen any other civilizations because of light speed. Hundreds, thousands, or millions of light years away means that is what we would see. And vice versa. If there was a planet with intelligent life light years away, if they had an insanely high powered telescope to view onto our land when no clouds covering, the distance away would be how many years in the past they were viewing. They would not see us today, but hundreds, thousands, or millions of years ago.
Unless we ever developed the technology to travel faster than the speed of light, we will never get very far either. Same for other life elsewhere. So perhaps there is intelligent life on millions of planets right now but we won't see it in our lifetime if all began relatively the same time.