Trope-a-Day: Sufficiently Advanced Alien
Sufficiently Advanced Alien: The Precursors and other elder races were, in their time. Whether or not they still are, or would be if they somehow came back again, is… debatable, and depends heavily on exactly how much physics lies between the current state of the most advanced known technology and the remaining “inexplicable” Precursor artifacts.
On the other hand, by far the majority of Precursor artifacts are now pretty well understood (see: Older is Better), so it’s likely that galactic civilization could give ’em a run for their money if they did somehow turn up.