> export default () => <div>{1+1}</div>
is
export default function () { return React.createElement('div', null, 1 + 1) };
If your concern is for beginners, I can appreciate that. But for anybody developing an enterprise grade application, using a transpiler isn't an appreciable barrier to entry. For beginners, there's create-react-app, vue cli, and angular cli. So you can get started immediately, without even knowing what a transpiler is.