I think it's like exoplanets. They were hypothesized on the basis that based on observation at that time they could neither confirm nor deny the existence of planets outside the solar system, and that the sun having planets couldn't have been that unique. It's just that it was believed that we wouldn't be able to observe these exoplanets directly.

The same thing goes with alien life. We have no conclusive evidence to deny extraterrestrial life, nor (to the best of my knowledge) conclusive evidence to confirm it, and it's highly unlikely that the Earth is that unique. The question is whether we will be able to confirm the existence of alien life, and while that enough is thrilling, will humanity be able to interact with them within our lifetime. My guess is that sometime in the future we will have a breakthrough and we will be able to at least confirm the existence of extraterrestrial life beyond doubt.