You still need something on the server to fullfil your requests, from that point-of-view your rest based controller receiving the JSON is still part of MVC. The view is the JSON representation in this case. So MVC or the server-side part of things is still relevant. Now the discussion on whether to use Reactive or traditional style programming is a different question that isn't answered easily. As reactive is a totally different programming model changing the architecture of your application, it isn't for everyone.
I am a man of mystery. Mostly because of this tiny ad: