i think that such entity is actually entities, in the sense that if there are intelligent species, we can be sure that there are lots of them, not only one.
Very likely, the universe is big enough to contain everything you hypothesize, and yet much more.
We tend also much to see this subject as an interaction between human and "others", when actually it makes much more sense that these different entities interact among each other.
Why is the human race and Earth in general being somehow "ignored"? Some users talk about our tendency to kill and make suffer each other, and I think that it's the right track.
If there is a condition by which such "advanced" (again, we focus on technology, but i suspect that it's a much more general aspect) beings can't or don't want to, approach the humans is that humans are divided and do not act with a single will, which should be the "most general good possible" at their level of culture, society, etc.
I sincerely doubt that anybody who is able to perform voyages over light years distances would enter in contact with our current leaderships - so that they can keep it secret and try to exploit it to their advantage and to the disadvantage of the other creatures of the Earth.
There is also another problem, and this one is pretty much "human only" - religions. The disclosure of the knowledge that we "aren't alone" would force all the human religions to readapt to a much more universal context. It would also probably mean that some of them, especially some of the monotheistic, would be subtracted of most of their fundamental reason d'etre. The way human matters are managed these days, I don't think that such adjustements will be allowed in any short period of time.