Would we know if they were?
Are aliens extinct?
Not until the wall goes up.
Who knows ? I think Space agencies such as NASA , ISRO,RSC itself struggles to find the answer , since universe has no end and distance between the galaxies are so much light years apart we are finding difficulty in finding them, we also received a signal called WOW! Signal from outer space may be the aliens might have sent them to us we are also sending signals to the space , who knows, the world that are likely got to receive our signals might get destroyed before our signal reaches them that might be the problem , but one thing for sure we are not alone :)
I think we have to establish they exist first. I'd say there is a good chance there is other life out there.
Take a real long look at the human race,
and you have answered your own question.