I think the scenarios for alien contact you lay out assume too much that the aliens think and act like we do. If there are galaxy-traveling aliens out there and they made contact with us, I think it might be hard to distinguish their contact from some kind of cosmic cataclysmic event - imagine an anthill that sits near where they're building a highway. From this POV, the "good ending" is one where we are coincidentally unaffected by contact and can even use the observations we make during it to advance ourselves a bit, and the "bad ending" is the one where we get paved over by a civilization that doesn't even realize we're here.