It is indeed unfortunate, we can only detect aliens with similar cultures and technologies to ours. It's sort of like only looking for your lost car keys near rhe lampost, because you couldn't see them anywhere else anyway. Unforunately, it appears only technologies capable of sending electromagnetic radiation across interstellar ditances are detectable. As far as we know, nothing else ibesides EM capable of traveling from star to star.

It is possible to conceive of other technologies not based on physics that could drive highly complex civilizations which would be totally invisible to us. For example, instead of electronics, an intelligent species could have mastered chemistry, the way our insects have. They are incapable of thought yet can use pheremones for communications in ways our chemical engineers can't even touch. Maube aliens can't build spaceships, radio telescopes, or comm lasers like we can, but they might have biological computers and chemical machinery far superior to ours. Instead of building clever devices, maybe they use their brains to construct efficient, robust, humane and prosperous societies. They would view us as dangerous, quarrelsome children armed with dangerous weapons.

You know, the more I think about SETI, the more of a fool's errand it appears to be. It's so sad, because it would be so wonderful to find someone else out there, but the more you think about it the more it seems SETI is only a means of finding someone just like us.