This famous quip generates a lot of thought. To me the answer seems rather obvious. Space is HUGE. The distances between stars are VAST and many probably most planets are uninhabitable. Other planets are years, even decades away, even moving at light speed, as electrical waves do.
Earthlings have been emitting radio waves for about 100 years now. So only planets within 100 light years have any chance at all of even knowing we are here. With each passing year however it becomes likelier that some alien civilization will discover us.
But wait! It gets worse! Even if “they” hear our faint 100 year old radio emissions, it would take them as many years to get back to us, at least, as we took to get to them!
Where are all the aliens? Simple. They don’t know we’re here. They can’t know we’re here till our radio waves reach them. And even then however long it takes for them to hear our faint old radio signals (and decode them): it will take that long for them just to get back to use using radio waves, to say nothing of their inevitably much slower space ships.
Likely we will discover or likelier be discovered within 1000 years. Maybe even as few as 100. But likely no quicker than that, unfortunately.
https://www.popsci.com/where-are-aliens-new-model