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.
Magic From Technology: Played straight; it is a materialist, science fiction universe; any magic we see is, indeed, one or another form of technology, misunderstood. Which seems to happen with truly annoying frequency every time a Sufficiently Advanced culture runs into an Insufficiently Advanced one, especially with any technology that doesn’t have big obvious machinery associated with it.
This is annoying as hell to most of the people on the wrong end of it. (The Imperials, in particular, hate being stuck with the “magic” label because of several reasons, primary among which are disliking falsehood, disdaining the respect of people who are basing it entirely on ignorance, and being proud of actually understanding every tiny nuance of what they’re doing at its real level of complexity, and therefore considering having it labeled as “magic” to be depriving them of their rightful awesomeness, dammit.) There’re always a few who are inclined to try to pull the “We Are Mighty Wizards – or Gods – from the Sky, Now Give Us All Your Liquid Assets” scam, but it’s just so tacky.
Also, more to the real reason it’s less done than it might be, quite unsafe, given just how many expectations people have for their gods. After all, we nailed ours to a stick.