The important skill to learn is figuring out how to do it. Coding is no different. For example, I've yet to use React to build an app, but I have taken the time to learn the basics of how it works. If I needed to use it I could, and would, and it wouldn't slow me down much, if at all.
I think what's important is discovering how adaptable one is. If one gets whiny about using a specific toolset they're going to be a problem no matter what you put them on that requires something different than their existing skill set.
TripleByte has a very clear process which leads to a two-hour frontend interview, an hour of which will be dedicated to building something with React.
Give it a try: https://triplebyte.com/iv/NKCtNG2/it
You’ll surely learn something.