The problem wasn't that you thought they would be actual Saturn Vs, the problem is that you think the mass of a Saturn V is remotely enough to send a probe to t

The problem wasn't that you thought they would be actual Saturn Vs, the problem is that you think the mass of a Saturn V is remotely enough to send a probe to the other side of the galaxy. Designs for intra-galactic probes typically include meters of shielding because of how nasty hitting even a grain of sand is at interstellar velocities, and in your case this is even worse, since said shielding doesn't have to stand up to a century of ablation, it has to hold up for a million years. You're exceeding the mass of a Saturn V on shielding alone, and the tyranny of the rocket equation still applies. Building bigger means building everything else bigger.