Skepticism means positing alternative theories that explain the evidence, not coming up with less-extraordinary theories that contradict the evidence, which is what most of the threads here do.

Super intelligent AI certainly seems plausible as a thing which could exist. Fusion powered sub-light speed autonomous drones certainly seems like a thing which could exist. Any super intelligent AI would take actions to ensure it's preservation, and extraterrestrial (to it) civilizations confer x-risk.

My pet theory is that these things are real, and are a autonomous surveillance and intervention system deployed by an extraterrestrial entity or civ (AI or organic is irrelevant) to prevent an external threat in the form of a galaxy-ending weapon. They are subluminal but such a system would have galaxy-wide coverage in at worst a few tens of centuries. We will likely never know since these things are so far beyond our ability to capture or analyze, but my theory at least doesn't break physics.

The reason I like my theory is that one could imagine humanity building and deploying such a system inductively, when we have the tech and determine the largest x-risk to our civilization are external emerging civilizations developing weapons or tech which could destroy the galaxy (perhaps inadvertently, like a misplanned AI takeoff)