Either the question is disingenuous, or you just don't understand that the choice of UI framework (such as React) has no significant impact on the visual design of a site or app. There are caveats, because certain paradigms can make implementing certain designs more challenging, but for the most part they are unrelated.
Now you are assuming he doesn’t know what he’s talking about. The choice of framework can certainly affect performance, especially for UI interactions (which is the case with reddit), and might encourage patterns (for example, async loading everything) that can have significant impact on the user experience.
