Earth like systems are exceedingly rare, you need the perfect conditions to get a long term habitable planet capable of intelligent life that can exploit fire/chemistry (A frozen ice world might yield intelligence on the order of a whale but whales can't forge underwater). Jupiter keeps us from being swallowed by the sun, it protects us from asteroid impacts...All the other systems we see last I checked are binaries or gas giants in close orbit (or some other unique outliers). Furthermore you need a moon to mix and stir the primordial tide pools and churn down the rock and later mud.... you need a magnetic field or everything gets cancer and dies, you need the right range of gravity or else you'll get nothing but slugs... There are so many conditions you need to meet and the distances between these systems are so large. The only way they get here (or we get there) is a Rama style generation ship that we could see coming for years and years. The most realistic scenario is just long range/high delay radio communications. Unless the aliens can literally break physics we would have nothing to fear, and if they can literally break physics there are plenty of other places to get metals and water and whatever else you want. You would need a hyper advanced race of slavers (and what do you need with us anyway if you are that advanced, unless they are all jewish alien sex pests) or predator style sport hunters willing to spend untold billions to mount a naked ape on their wall. They are out there but they are way too far away and just as limited as we are so of course we haven't discovered them.