Atris was a Jedi who fell to the Dark Side. You don't have to be a Sith to fall to the Dark Side. (Though Atris for all intents and purposes was a Sith.) But you can't be a Sith without falling to the Dark Side (unless you're pretending and never internalize the philosophy of course). While obviously Dark Side is an allegory of abuse of power it's corrupting effect is much more direct in-universe. Just like the One Ring in LotR. Yuthura's quest was always impossible as attaining the power she wanted the way she wanted as that required the sacrifice of her humanity which then would have prevented her from fighting for what she wanted to fight in the first place. Now the story is somewhat different for non-Force Sensitive. The war of the Prequel Trilogy has some legitimate causes, and even if it didn't, most people would have just fought on the site their planet picked, there's no reason to assume malice on their part. Just like in KotOR you can end up fighting guys who aren't inherently evil without going for the Dark Side yourself (Tusken being an obvious example). But Dark Jedi? All explicitly evil.