> React becomes counterproductive when developing apps that aren't mere demos.
I have developed big apps in Backbone, moving very the same apps to React and the productivity went up madly. Facebook does develop apps which certainly cannot be considered "mere demos" and you can see them in action, for example Ad Manager for Facebook on iOS (written in React Native). Facebook invests a lot in React development and there is a reason for that - they use it internally intensively.
> It's marketed to developers by billion dollar Facebook, a company historically intent on squashing startups.
This is not an argument at all. I would be really surprised that's the reason for React to exist. Also React is more a way of thinking, the library itself can be replaced if Facebook should enforce it on a successful startup.
> The utility gained by using React's ecosystem is significantly outweighed by its overhead.
This is certainly not my experience. React has very little overhead and from my experience it's pretty easy to grasp the concept for new developers.
I have no idea where does hate for React come from, it's >> just << an open source library and I wonder how people are willing to start flamewars about a few lines of code. If you don't like React, don't use it. There are a few alternatives like Ember, Angular or even Backbone (although I would say Backbone deserves much more hate than React).