Except you're wrong. You're viewing this through a logical perspective, not an emotional one: i.e, you're thinking about how things should reasonably sound, but not actually including the emotions and behaviors of how real people would act and behave. No sane person would ever trust Zinnia because she dresses like a ragged homeless man, often sports a psychotic grin, and acts very patronizing and barbaric despite never offering any evidence to back up her claims.
Meanwhile, Steven might be a bit of a tool but he and all the scientists actually DID provide factual evidence in-universe to support their theory and solution to the problem. They had actual proof they provided. Zinnia just goes off on a "MUH IMAGINATION" tangent and then smashes the link cable, despite proving literally not a shred of evidence other than "lol dudes trust me".
I mean, if you met a psychotic women in tattered clothes who talked like an absolute lunatic, would YOU want to give them a moment of your time? No, you'd tell them to go fuck themselves.
And let's not forget she:
-Told Team Aqua/Magma how to awaken Kyogre/Groudon in hopes of getting the fug to show up, despite the fact it could literally cause the end of the world.
-She did this despite showing you that in ancient times, Rayquaza only ever showed up to stop Groudon and Kyogre fighting when BOTH of them were present, meaning that she could have easily seen it wouldn't have worked even by the logic of her ancient history and still went through with it because she's a crazy bitch.
-She broken into peoples houses and assaulted their children to steal their belongings.
-Knocks the player out hard enough to leave them unconscious for an entire day.
-Knew that Rayquaza was a territorial no-bullshit monster and expected it to listen to her.
-Runs away from the mess she made when you fixed it for her sorry ass, and still doesn't think she did anything wrong.
Stop thinking with your boner and start thinking with your brain.