I mean our sun is 4 billion years old, it took that long for us to show up and even contemplate the possibility of a Von Neumann probe, we may or may not build

I mean our sun is 4 billion years old, it took that long for us to show up and even contemplate the possibility of a Von Neumann probe, we may or may not build one someday. How do you build an autonomous system which is rated to last and self-replicate for, say, 250 million years, until you've done a few trial runs which lasted about that long? The universe is only 14 billion years old to begin with and the Milky Way has hundreds of billions of stars to explore... the math is admittedly above my pay grade, but if you assume ultra-advanced technological civilization is rare and interstellar travel is only possible at a small fraction of C, it seems plausible enough to me that simply no one has managed to send Von Neumanns into our neck of the woods yet. The hypothesis handwaves the question of whether such an invention is even possible.