The 2000s cartoon style isn't accidentally kid-coded — it's nostalgia-coded, for people who were kids when Kim Possible/Danny Phantom/Ben 10 aired. Those people are 28-35 now. That's not a mismatch with your concept, that's a second, completely real audience: adults who grew up on that visual language and will feel an immediate, specific pull toward it — the same instinct driving the huge adult market for "kidcore" aesthetics, nostalgic merch, adult coloring books, Stranger Things-era 80s/90s throwback demand. These are people with disposable income who buy things for themselves, not just for kids.