You are quoting Carl Sagan. I am quoting another Harvard astronomer, Avi Loeb.

What Loeb is pointing at is that in the real world you can't expect extraordinary scientific evidence while refusing to fund the research that could produce such evidence.

I am not claiming that these observations are caused by aliens. I am merely pointing out the inherent contradiction behind statements like "we don't know what this is, but [we sure know] it is not aliens".