If you read “The Hitchhiker’s Guide to the Galaxy”, you’ll see Goonhilly gets mentioned right at the beginning for failing to spot the Vogons! So now, we keep an extra special look out for them and other aliens.
They are probably out there….. but think of this…. we have been broadcasting radio signals for around 100 years. How far out into space will those signals have reached? How many stars will that cover?
There might be aliens but they’ll be difficult to find.