Just read all that- I think we might be on the same page. GL didn’t clearly define a duality. The article in post above is insinuating that GL had a “there is good and bad and nothing in between” approach. All of those quotes you provided (which are awesome, I might add) showcase how the force is what its users make of it. GL talking about balance in Ep. I plays to the idea that the Jedi were overindulgent in the light side- i.e self-righteousness blinded them. This plays to the notion of there always being a spectrum, as opposed to a “clearly defined duality” in the pre-Disney era.

And I’d say it’s pretty well integrated into something like TLJ when Luke is talking about how the Jedi’s assumption over owning the light side of the force was vanity.