So framing it as a disagreement makes it sound like conflict, and while that happens every now and then (people are people), I don't think this is really about internal conflict, and will propose an alternate framing:
Your content strategy and your balance strategy must be in sync with each other.
As a dev team, you're creating all this content for a reason: you are creating moments, creating memories, inviting new players into the game, whatever the exact goals might be. For League of Legends, new champions are expected to make a mark on the ecosystem.
If League's balance strategy says that we're going to change and tune champions until they win the same number of games (it doesn't, but at times it hasn't been that far off from saying that), then I can guarantee you that no matter how well designed your next simple champion is, they're going to be forgotten 3 months later. If Naafiri and Sylas are winning the same percentage of games overall, Sylas is simply more powerful than Naafiri is and players will pick up on that fact.
And if your simple champions usually fail to make a mark, you're going to be left with a community wondering why you only make complex champions - because those are the only ones that come to mind when you think about new champions. And if you fail enough times at achieving goals with simple champions, you're going to make them less often.
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