According to Thor, the Asgards had barely scratched the surface of an Alteran repository, and that was after a very long time of research.
Yeah, the Alteran databases were designed to interface with Alteran brains, and
only Alteran brains. Humans, being technically an Alteran subspecies, are theoretically capable of understanding the contents of Alteran databases if their brains could handle the strain of so much knowledge. But the Asgard had to basically manually decrypt everything in the database piece by piece, and Alteran encryption is ridiculously good; for compression purposes rather than security purposes, but it works for security as well.
So despite having the Alteran database for millions of years, plus whatever the Alterans shared back when they were active in the galaxy, the Asgard have only worked through a small part of its contents because the system just wasn't designed with Asgard in mind.
We still have no idea what physical characteristics, IF ANY, correlate to higher intelligence.
Not entirely true; certain characteristics
have been shown to at least correlate with intelligence, though any potential causation is still up in the air: Synapse quantity\density is the most obvious, people who rank highly for 'intelligence' almost always have an above average quantity of connections between neurons.
Whether this is a cause or a symptom is unclear.
Except that, you know, the plague had nothing to do with losing to the Wraith, because it's why they went to Pegasus in the first place?
The Atlanteans lost because they didn't do their best to hide for a few thousand millenia, building up their drone stockpiles, until they could reappear with a million drones for every Wraith dart.
Because they had the technology to do that.
But not the attitude; as we can see from the many, many,
many unfinished projects the Ancients left lying around, including an
entire engineering team that had completed the work on Destiny and gone into stasis, expecting to be retrieved by their kin later on when the Destiny was 'activated', which never happened.
If they had tried to hide for a few thousand years, building up their weaponry, they'd probably have forgotten entirely about the Wraith before the end of the first century and been distracted by whatever SCIENCE! project they were currently working on.
Expecting the Ancients to stay on task for any significant length of time is a fool's errand.