Huge starships enter solar system, consume Pluto, begin harvesting Uranus, at current rate will reach Earth in 100 years
Most stories of alien invasions have the aliens making a beeline for Earth. Sometimes they want to help humanity, sometimes they are just explorers, often they want to take off. But an alien civilization might not be especially interested in either Earth or humanity. If they’ve adapted to life in space a habitable planet (for us) could be just another curiosity. Planets could simply be sources of resources.
And what would humanity do if we knew a technologically superior “enemy” was coming? Band together? Fight more? Invest in defense? Try to contact the invaders?