You're allowing a lack of evidence to be evidence of the negative.
The incredible vastness of the universe means it's incredibly unlikely we're the only intelligent civilization in existence. But the incredible size of the universe also means that any radio signals being emitted by said civilizations haven't reached us, and even if they did, they'd be so weak they'd just be background noise.
A picture with 1 billion galaxies...each with millions of stars...each potentially with any number of planets...it just seems really unlikely that we're the only ones out there.
But even if we somehow proved another civilization exists, outside of the knowledge that we're not alone, it'd be meaningless. They're way too far away to observe, let alone communicate with.
