You appear to be claiming that there's an infinite amount of explanations and we can't really know, while also claiming that more data points don't create greater certainty of correlation.
That's contrary to the basis of how science works.
I did not claim the part about more data or that we cannot really know, but rather that if you have to consider any and all explanation in an analysis you have a problem - it's a line of thinking that doesn't help and leaves the realm of science.
For example, is having a simple mechanical explanation for something really evidence against some Devine intervention that is just done so that everything looks "normal"?
Why do they have to travel to earth ? A robotic probe can travel X thousand years with no need for new physics. Also there are life forms on earth that basically live forever. Also pretending that a theory that we invented a 100 years ago that is not even fully consistent is some hard limitation on some advanced civ is pretty crazy. Is it more believable that some entity on earth has discovered new physics and kept it secret vs some advanced extraterrestrial civ is more developed than we are ?