Routing, http, and models aren't hard problems. Blaming React for not being an entire MVC framework is silly. It's not designed to be, and there are any number of ways to solve that problem.
Being able to use it with ANY different set of solutions for MC is especially good. I can use React for UI on top of old jQuery pages if I want to. I'm not forced to change my entire application to use it.
Decoupling is a really, really BIG benefit, not a downside.