We can barely see other stars, and have only recently confirmed the existence of extrasolar planets despite that being basically a given. What artificial structures would exist that would be detectable at that (non)level of clarity? The only thing we can detect at this moment is something capable of meaningfully interfering with a star's natural EM radiation output.

Dyson Spheres are theoretical and arguably not terribly useful or desired, and no known substance has the strength to build one or anything remotely on the same scale without tearing itself to shreds. Dyson swarms are easier to build but still unfathomably massive undertakings, and might not noticably detract from a star's output from the perspective of a telescope light-years away. Anything else is too small to matter for this question.

Furthermore, space is almost perfect at hiding signs of intelligent life. The distance between neighboring habitable worlds is measured in light-years, and the best long-distance form of communication we have (radio waves) are drowned out by several orders of magnitude by naturally occurring sources of radio waves like stars.

Basically we have no idea how common life, intelligent or otherwise, is in the universe and there's no way of confirming one way or another unless someone in our immediate neighborhood decides to abuse the Kardashev scale for shits and giggles or we invent FTL communication/travel and go look for ourselves. We may or may not be alone, but the difference is academic; we're stranded on an island with no radio and there might be an island full of people just over the horizon, or there might not be.