What was the laser beam spread from Earth to the moon? Something like a quarter mile? At a quarter mile at 250k miles how wide would the beam be from millions of light years away?
A bit more than that. 6.5 km or 4 miles.
Not to mention that they would have know about Earth, and know there was life on it, and aim their laser just at the right point in anticipation that our planet would be at this place at this time to receive it.