I like Sci-Fi and aliens as a sub-genre.
My objection to aliens is that there are four options only really:
1) they don't exist, we are the only sensient species in the universe;
2) they exist, travel between star systems is possible and they simply don't have the technology like us;
3) they exist and regardless of their technology level, travel between star systems is physically unachievable for living beings;
4) they are here, but so well disguised we can't differentiate from other human beings or we can't see them (or Descarte's daemons theory: "what if the universe is an illusion so perfect we can't distinguish it from actual reality?")
This is the only reason why they wouldn't be swarming on this planet right now in some form colonialism. Any alien that we would be able to relate to as sensient beings, would probably be as inquisitive as we are, we the similar ranges of moral reactions towards us, and there would be those who were on our side, those who would be "racist" against us, imperialists, etc etc.
But we see none of that. So only 1 - 3 are possible, or 4 makes it irrelevant that they exist, since they don't do much more than posing as perfect illusions.