Lucas himself kept it pretty simple. From interviews and the movies themselves, his narrative is that the dark side is a corruption and abuse of the force. Think like burning through natural resources, instead of using renewable energy. The Force is not a finite resource in that way exactly, but corrupting the Force can have wider effects psychologically and sociologically. This may seem overly simple at first, but I don't think it is when you consider just how evil the Sith actually are.

But you know, death of the author and all that. The expanded universe saved Star Wars in my opinion, and gave it a lot of much needed depth. There was a lot of info about lessons Luke had to learn about accepting all parts of himself, and learning how fear, even of himself, leads to the dark side. He hesitated using powers like force lightning or mind manipulation because of how evil it seemed. But he learned that it isnt an act itself, but the intention behind it that matters, as well as the reasoning/wisdom behind it. Dominating another's mind to aura farm or assert your authority is not the move, but a Jedi mind trick to save lives is acceptible,for example. This was expanded in more in the EU by those that walk a middle path, the Grey Jedi. Who were not all that different than Luke ended up being, though they were more fixated on the whole "duality of man" thing.

The Prequels reinforced this by highlighting how imperfect and ultimately impotent the Jedi order was at the time of Palpatine's rise.

While I don't believe the discourse online that Anakin killing all Jedi and Sith WAS the balancing of the Force, the Jedi Order DID need to be reworked. Just like how religion in real life isn't perfect and needs reform kn a regular basis, but we do need people to tell us to be nice to other humans and form a certain kind of worldwide standard of social accountability, and religion is a useful form of that. We certainly DON'T need an equal, "balanced" amount of people whose religion is mass genocide and "might makes right" to the degree that they kill their teachers (often guardians that raised them) as a rite of passage. Also, Jedi=/=good the same way religion=/=good. The Light Side is good. The Jedi, and religion, attempts to achieve goodness, but does not always succeed. The Dark Side, whether Sith or Dark Jedi, is fundamentally a rejection of accountability, the concept of goodness, and respect for the natural order of the universe. This so-called binary, ironically, comes from the idea that anything not approved by the Jedi order's dogma is the Dark Side.

This overly emphasized social pressure is a big reason Anakin fell. In his mind it was "well I did x so I'm not a Jedi anymore, so that means I have to embrace the complete opposite of everything I once stood for because I am now officially Bad™️". And while Anakin is responsible for his own actions, the Jedi Order is not "good" either for setting him up to fail like this. He seems like (and is) an idiot who was easily fooled and manipulated. But like, Padme was the only one who fully accepted him for who who was, even after he admitted to thr Sand People massacre. She never even looked at him with fear or judgment. Palpatine was similar. And that's a powerful thing.

But none of this means the Force decided "we need some more genocide and less people who care about trying to be good. Send in the chosen one." That's just dumb.

I'm not going to pretend there was any subtext to the sequels since there isn't even a main text.

Source: used to be WAY too much of a Star Wars nerd.

EDIT:

In the scene you mentioned, Yoda warns him not to take his weapons, which Luke ignores. When Luke asks what is waiting for him, he tells Luke "what you bring with you". Bringing weapons/violence to "win" at his training is missing the point of what Yoda was trying to teach him. Obviously violence IS sometimes necessary, some people are too far gone, and Yoda himself later tells him he'll need to defeat his father. But the lesson is this: when your main tool is a hammer, everything looks like a nail. Luke learned the lesson, and by committing to the bit while staring death in the face, was able to save even Vader.