I think there could be a combination of things going on. Your argument can be statistical rather than absolute. We may not be alone in the universe, but to becoming universal explainers might be so rare that when you start multiplying that by interstellar distances,. which are quite vast. And i think farme also had the unreasonable assumption that interstellar aliens would figure out how to get past the speed light - we have no hypothesis whatever as to how that might be possible.