From that Facebook article: Flux eschews MVC in favor of a unidirectional data flow.

This is so incorrect. MVC doesn't imply two-way data binding. The whole Flux architecture was based on a misunderstanding of MVC, and is therefore questionable.

Most UI frameworks, including iOS, ASP.NET Core, JSP and JSF (Java based frameworks), Ruby on Rails, and Django (Python) are all based on MVC.

Why is it that MVC works for all these other frameworks, but doesn't for React? The answer is that MVC does in fact work for React. React itself originally used the tagline "React is the V in MVC". Flux/Redux introduce needless complexity and unnecessary boilerplate. There are MVC libs that make React much easier to use.