We can't know what's wrong yet. We'll see once people start using and exploring alternative frameworks. It's arrogant to think that React did everything correct. Even in React itself we've seen some evolution (React.createClass -> ES6 classes -> ?pure functions?).

But that's not what the post said - it said wrong in comparison.

Also your class creation example is just talking about language semantics. It'll never be a pure function (can't be - has to hold state) but it IS a pure object under the hood.