Isn't it fairly obvious that any civilization that came to Earth from anywhere outside of our solar system would have to be far more technologically advanced than us? In fact, it's necessary that they are or they could never propel themselves the distance in any reasonable amount of time or survive the journey. Our current technology is hardly capable of effectively reducing the enormous risk posed by cosmological radiation and potentially devastating micro-particle collisions in the short term let alone during an interstellar journey, not to mention the sheer logistical problems of navigating space (you can't just launch and aim toward your target even during interplanetary travel). The fact of the matter as it stands is that there may be life somewhere else in the universe, however, considering the vast distances and physics, even if there were sentient life and we intercepted a radio transmission, from what we know of the nearest planets that may be capable of supporting life, it'd be so far away that when we received any such transmission whoever sent it would be very, very long dead. Second to that is how any other civilization could know of our existence as our most distant radio broadcasts have made it only about as far as 80 light years. The most distant and currently the only signals from Earth that are in interstellar space. If any civilization made it to Earth themselves, I'd want to know how long they'd been in travel, because the nearest star to Earth is itself 4 light years distant and the most distant man-made object from Earth is Voyager 1 (10.5 billion kilometers) launched in 1977 and it's also the fastest which is still pissing slow relative to even interplanetary distances (it'll be interstellar in a few years).
So, yeah, just why does everyone think that any civilization that visits Earth would have to be more technologically advanced than us? You answered your own question only what you added is plain wrong. They won't likely reach us ever.