I see React as a tool for building web applications, not websites. Using it for something like hacker news is not needed nor worth it, except for learning purposes or for the sake of using your favorite tech (which has its pros and cons).
Edit: I use React a lot, and really like it. It's just not the perfect tool for everything, and by no means a necessary one (at least when you don't have much complexity); even if it is a good one in many cases.
In the case of HN, seeing the current js [1] I find it pretty obvious that no "big tool" like React is necessary. It doesn't mean using React for a HN clone is a bad thing, one just don't have to.
[1]: https://news.ycombinator.com/item?id=17915560&goto=news