It’s not a plot hole, its the emotional thrust
The criticism I read the most before seeing 2017’s IT was that the kids don’t tell each other about the monstrous hallucinations that IT attacks them with.
But they also keep the real world, non-IT abuse secret too. Bill is a stutterer who is haunted by the memory of his brother Georgie’s disappearance. Beverly has an abusive father and the entire town conspires to demean her with cruel rumors and sadism. Eddie’s mother tells him lies to keep control of him. She isolates him. Convinces him he’s sick. Ben is smart and curious and bullied for his interests and weight (something that is never portrayed as funny. When their insane schoolmate Henry and his bully friends attack him, it’s framed as ugly.) Mike is a sensitive boy who’s an outsider even by the standards of the much-maligned Loser’s Club. Black, homeschooled, orphaned, him and his late father both victims of racist law enforcement grudges; he works a job that demands he harden his heart to survive. Richie is a goofy oddball wanna-be comedian. Stanley is Jewish, more affected by the violence of fear than the others.
They’re all vulnerable kids and at every turn, people take pleasure in reminding them that they’re small and weak; that their abuse is warranted. That it can never be overcome. They don’t share any of those abuses with each other either, only make passing references to their fucked up circumstances through jokes.
It isn’t until Beverly shows them the bloody bathroom from a geyser of hair and blood that attacked her, until she opens up about something horrible that’s been happening to her, that they’re able to come together as a team. Her father is unable to see the blood. But her friends do. Even if it isn’t real, even if it’s only a hallucination. They clean with her. It’s plain in the final confrontation with Pennywise, where they rescue each other and beat IT into submission. You can’t always overcome your fears alone, but you can help others overcome theirs.
That final fight mirrors the scene where the Loser’s Club goes feral and throws rocks at their bullies. They’re standing up for themselves. They’re defending each other. It’s one and the same.
It’s a story that never fails to get to me: misfits joining together to overcome tyranny. Terrorism is a tactic of the weak and it depends on scared people never opening up. If everyone is scared and everyone’s afraid to admit it, then tyrants keep their hold on them. That’s Pennywise’s game.
“Ain’t nothing like a little fear to make a paper man crumble.” Is what Henry’s dad says after he shoots his gun at his trembling son’s feet. (Henry too is a product of abuse. Though he uses his pain to fuel his sadism and in so doing is easily seduced by Pennywise, who offers him power.)
Fear is also the weapon of a paper man. It’s cheap, sad, easy. But also undeniably powerful and easily stoked and self-propagating.
When the Loser’s Club gets ready to enter Pennywise’s lair, Stanley hesitates at the threshold. But the other boys convince him to come along. “We all have to go…if we stick together, all of us, we’ll win.” They need him. And more importantly they won’t leave him behind. Their camaraderie is stronger than fear. And it’s stronger than Pennywise. And it’s stronger than Derry.