Both. Humans are fundamentally a social animal, Rousseau's "State of nature" doesn't really exist.

Both society and humans are also the cure though:

• All individuals have the ability to discern and to choose good
• Society can teach what is good, and our tendencies to watch out for, and for the most part it also does this.

I don't believe the flaw can be eliminated, nor that the attempt would be ethical. Perfect is the enemy of good, you should teach people as best you can, but in the end still let them choose, anything else is thought-stopping cultish totalitarianism.

I like the quote from Terry Pratchett, (Granny Weatherwax)

And sin, young man, is when you treat people as things. Including yourself. That’s what sin is.

I think the worst parts of society, and innate "laziness" leads people to treat others (or yourself) as things, but that it's also innate to "know" not to treat others (or yourself) as things.

I don't believe the flaw is hopeless, even if it stays with us forever (at the individual and societal level).